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Pulp & Paper Solid Waste Initiative Phase 3: Sector Level Technology Options Summary

Kim McGrouther, Suren Wijeyekoon, Murray Robinson and Robert Lei from Scion. Chris Purchas and Sam Bridgman from SKM. Author contact: kim.mcgrouther@scionresearch.com

Pulp & Paper Solid Waste Technology Assessment

21 June 2013.

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Supported by the Ministry for the Environment’s Waste Minimisation Fund.

Acknowledgements Developed as part of the NZ Pulp & Paper Solid Waste Initiative Project with financial assistance from the Waste Minimisation Fund, which is administered by the Ministry for the Environment; and from the pulp and paper sector.

Diclsaimer and Copyright The Ministry for the Environment does not necessarily endorse or support the content of the publication in any way. Reproduction adaptation or issuing of this publication for educational or other non-commercial purposes is authorised without prior permission of the copyright holder(s). Reproduction, adaptation or issuing of this publication for resale or other commercial purposes is prohibited without the prior permission of the copyright holder(s).

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Pulp and Paper Solid Waste Initiative

Phase 3: Sector Level Technology Options Summary

This summary of technology options relevant across the Pulp Processing Sector is the culmination of methodology development (phase 1), data collection (phase 2) and options workshop (phase 3) for the NZ Pulp and Paper Solid Waste Initiative.

The NZ Pulp and Paper Solid Waste Initiative is funded from the Ministry for the Environment’s Waste Minimisation Fund (WMF). In addition to support from the Waste Minimisation Fund, the project is financially supported by Scion, CHH Pulp and Paper, WPI and PanPac. Norske Skög Tasman also supports the project through provision of solid waste data related to its operation.

The first phase of this four phase project focussed on developing a methodology for technology evaluation and data collection and summarising waste management technologies relevant to the pulp sector in New Zealand. Technology sheets and the methodology framework provided the platform for phase two and three of the project.

These are published on the Scion website: (http://www.scionresearch.com/research/sustainable-design/environmental-technologies/pulp-and-paper-solid-waste)

The development of a waste strategy and action plan has four inter-related phases:

Phase Deliverables

1. Methodology and Technology Options

Data Collection, Evaluation Frame & Technology Sheets

2. Mapping Industry Solid Wastes Sector data summary

3. Options Analysis Industry Options Evaluation

4. Reporting

Industry Strategy - National Data - Options - Preferred Options - Business Case(s) - Action plan

Prior to the sector level options workshop, the project team from Scion and Sinclair Knight Merz (SKM) held company focussed workshops with representatives from the individual mill sites1 around New Zealand to discuss the options for reducing waste solids to landfill at their site. These individual workshops provided the basis for site reports and the discussion framework for the Sector level workshop.

1 CHH Penrose (Auckland), CHH Kinleith (Tokoroa), CHH Tasman (Kawerau), WPI (Ohakune) and PanPac (Napier). 2 Forestry statistics; quarterly production and trade information (2012) http://www.mpi.govt.nz/news-resources/statistics-forecasting/forestry.aspx

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Project background This project involves developing a simple model of solid waste flows from pulp and paper producer’s sites linked to potential users or treatment options for those materials. This information will enable businesses to identify opportunities to collaborate on treatment and use of waste materials providing opportunities to reduce waste management and/or input costs. The project is part of a longer process that will ultimately result in the improved management of waste (less waste to landfill, improved use of resources). To put this a different way the research into waste flows and treatment options is intended to be the first stage (feasibility study / business case) in getting one or more options implemented on the ground.

The focus of this project is to consolidate solid waste flows from a single sector. This focus improves our understanding of the key solid wastes from the Pulp and Paper Sector as well as providing information for solving national-scale problems created by solid waste from industrial sites. The project will provide business cases for investment where good opportunities are identified. These may form the basis for further applications to the Waste Minimisation Fund to provide capital funding towards the implementation of specific solutions.

Pulp and paper industry in New Zealand

The pulp and paper industry in New Zealand produces a range of wood-fibre based products and as a result produces a range of organic and inorganic wastes from their processes. To provide a feeling of scale for this industry, the pulp and paper sector in New Zealand collectively produced 2.36 million air dry tonnes (adt) of pulp, paper or paperboard product in 20122.

There are two different types of pulp mills in NZ, chemical and mechanical. The mechanical mills take wood chips and mechanically refine the chips to produce fibre. This fibre contains lignin and cellulose. Whereas the chemical mills use sodium hydroxide and sodium sulphide to produce fibres that have most of the lignin removed. The lignin is recovered as heat and energy when the pulping liquor is burnt in the furnace. The pulping chemicals are also reclaimed as smelt and reformed through the recausticising process. Both types of pulp mills recover energy from wood residues either from within or outside their sites. There are also two recycle plants in NZ, one in Auckland which recycles waste paper and the other in Tokoroa which recycles waste cardboard. The solid waste outputs from these processes are deinking sludge, plastics and other non-fibre contaminants.

The common elements with most of the pulp and paper sites in NZ are a central processing plant, an energy plant (which consumes wood waste and supplies energy to the process), a wastewater treatment system and either landfill or some form of further processing for solid wastes from the process. For the chemical pulp mills the central processing element is more complicated and produces a greater range of solid wastes than that from the mills using mechanical or recycle processes.

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Sector Options Identification

The identification of options for improved management of wastes at a Pulp and Paper sector level built on work completed by the project team for individual mills, a consideration of options relevant across the sector and feedback from the Project Partners (CHH, WPI and Pan Pac) at both these stages2. The identification and assessment of the sector options occurred as follows:

1. Identification of options for each site (site specific work)

2. Project Team (SKM/Scion) workshop to consider site specific options and undertake an initial evaluation process for relevancy as a sector level option

3. Project Team and Partners (CHH, WPI and Pan Pac) workshop to assess sector

options and complete an initial evaluation

4. Workshop summary notes completed and circulated (to be confirmed in the context of the National Strategy document)

The project plan originally laid out a timeline and approach to completing the sector level options evaluation using the framework developed for assessing site specific options evaluation. However as the sector level participants had already used the framework to assess site specific options (which fed the sector options) the focus of the discussion at the workshop was on how to progress options identified rather than use of the framework to identify options. Sector issues Sector issues were identified through data analysis and discussions at workshops. The first issue concerned what waste streams should be focussed on at the sector level. All sites, other than CHH-Penrose, produce ash (from burning of wood (bark, hog, chip and/or sawdust), and wastewater treatment residuals (made up of primary solids (fibre) and biological sludge)3. Figure 1 provides a sector level waste to landfill composition (full sector summary is available at http://www.scionresearch.com/research/sustainable-design/environmental-technologies/pulp-and-paper-solid-waste.) Because of the quantities of ash and wastewater treatment sludge waste produced at a sector level (40% and 28% respectively) it was decided that sector level initiatives should focus on options for the improved management (reduced risk, reduced cost) of these two waste streams. The second issue concerned the markets for recycled waste products. It was also made clear during the sector level workshop that the market for diverted pulp and paper sector wastes must be sustainable and of a size to handle the volume diverted. This means that, prior to development of technologies for reducing wastes to landfill, a market analysis must be undertaken.

2 The representatives from each company are Philip Millichamp (CHH), Gustav Bam (WPI) and Peter Allan

(Pan Pac). They are joined by Bruce Clarke (SKM) and Trevor Stuthridge (Scion) for matters concerning project governance

3 As a 100% recycle mill, CHH-Penrose only produces deinking sludge.

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Figure 1 Break down of % waste solids (wet tonne basis) to landfill from the pulp and paper sector in NZ.

Sector options

The focus of the option development has been on identifying options for ash and wastewater treatment sludge that reduce cost and risk. In some cases the materials are processed to produce a product with value (as nutrient or soil amendment). In the short-term these options are likely to be attractive if they are feasible (low technology, commercial, market and RMA/environmental risk) and available at comparable or cheaper cost than the status quo.

The ideal solution for these materials is where they have some value as feedstock, relating to nutrient value or soil amendment function. Taking the use of wood ash as an additive for fertiliser or soil amendment products, the solution may involve mill sites funding transport to a processing site or a paying a ‘disposal’ charge. Once the nutrient value of wood ash and the feasibility of blending are established the ash becomes a valued input into the final product and may have an impact on the market value of the product. This in turn may provide a basis for changes in commercial arrangements or result in multiple potential users of the material. This would be the ideal outcome from a mill perspective, moving from managing waste streams to having materials that are beneficially used at no cost to the mill or even produce income. Following consideration of key waste streams at a sector level the site level work was used to identify and evaluate options relevant across the sector. Figure 2 presents an evaluation summary of option feasibility; making use of the evaluation framework developed for the project.

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Ash For wood ash, the disposal options considered were: Disposal of ash to landfill (status quo as a benchmark); Utilisation of ash for fertiliser application4; and Use of ash to replace aggregate in roading or construction. For wood ash the evaluation suggests that the most preferable option for going beyond the status quo is using ash as an additive for soil amendments including fertiliser is an option. It is noted that ash characteristics, such as nutrient content, availability and particle size, vary between each mill (this is related to boiler design, feedstock and operation). The ramifications of this are discussed in the following section along with key barriers, opportunities and possible implementation pathways. Wastewater treatment sludge For wastewater treatment sludge the options considered were: Vermi-composting followed by land application; Direct application to land; Burning of sludge (ash requiring disposal/beneficial use); and Anaerobic digestion of biological sludge (residual solids requiring disposal/use). The evaluation suggests that burning for energy recovery and vermi-composting are the most preferable options because of the ease of implementation. The best decision for a specific site will depend on sludge characteristics, operational arrangements, boiler configuration, fuel availability and total heat requirements/capacity. Anaerobic digestion has potential, particularly for biological sludge, but requires proving in a New Zealand context. The evaluation highlights the lack of commercial scale application of anaerobic digestion to pulp mill sludge in New Zealand and the associated risk around finding an experienced technology supplier specific to the pulp sector. The key points to consider when looking at the evaluation summary in Figure 2 are that:

1. “Ash to forest” is where ash is applied on its own and “ash as an additive” is where it is applied in combination with a commercial fertiliser or as a blend with something like vermicompost.

2. Ash as an aggregate was ranked as a less feasible option because uptake by the construction or roading industry in NZ would require changes to standards to include wood ash.

3. Sludge burning was ranked as very feasible as this is already practiced in the pulp and paper sector in NZ and biomass boilers are already part of the mill energy infrastructure.

4. Anaerobic digestion (AD) is ranked with a low feasibility even though AD is a proven technology; the application to pulp and paper sludge is not proven.

4 Statistics NZ most recent Agriculture Census (2007) notes 3.8M tonnes of fertiliser was applied across NZ.

0.88M tonnes in the Waikato, 0.19M tonnes in Hawkes Bay and 0.35M tonnes in Manawatu-Wanganui. This means in the areas surrounding the pulp sector mills around 1.4M tonnes of fertiliser is applied to land comparing to approx. 55,000 tonnes (4%) of ash being available.

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Figure 2 Evaluation summary of option feasibility (Landfilling ash included as a benchmark). See Appendix A: Tables 2A and 3A for more detail of the scoring related to determining the non-price based feasibility shown above.

Analysis of Potential Technologies

Boiler ash and wastewater treatment sludge contribute approximately 68% of the solid waste to landfill for the Pulp and Paper sector in New Zealand. The boiler ash is made up of fly and bottom ash from combusting biomass and this is primarily landfilled (approximately 55,000 tonnes per annum). Wastewater treatment plant sludge is currently landfilled, vermi-composted or incinerated. There are a number of opportunities for increased diversion of these substantial waste streams from landfill. This section outlines the characteristics of the waste stream and potential diversion options for handling them. Boiler Ash Two types of ash are produced in biomass boilers – fly ash, which typically contains higher carbon and higher heavy metal content, and bottom ash which should be lower in carbon and heavy metals. Both ash types are alkaline and contain potassium, magnesium and calcium and sodium in considerable concentrations (gram per kilogram range). Wood ash also contains trace elements such as boron, zinc, copper and cobalt (milligram per kilogram range). According to reviews of applications of pulp mill solid waste residuals and ash from biomass boilers from the United States and America there are both land application and construction opportunities for wood ash (Bird & Talberth 2008; Elliot and Mahmood 2006; Monte et al. 2006; Pitman 2006 and Cavaleri et al. 2004).

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The decision whether to pursue either opportunity depends on a number of factors, such as:

• Ash characteristics o construction requires ash with <6% carbon o fertiliser application requires low heavy metals,

• Volume and logistics, • Access to land or construction/roading industry.

For the pulp and paper sector, diversion of ash from landfill will extend current landfill lifetimes. In this context seeking alternatives to landfill disposal for some or all ash is desirable. There are some site specific opportunities (reclaiming landfill airspace) as well as more generic opportunities related to reuse of ash based on nutrient, stabilising or aggregate properties. It is developing these generic opportunities that have the potential to form a sector level initiative. Ash to forestry/agricultural land5 The benefits of ash application to forest have been noted in Scandinavia and the US (Jacobson 2003; Vance 1998 and Pitman 2006). These authors have also noted that it is important to control the application timing and rate as well as treating the ash to improve handling. Ash handling and benefit to soil improves if it is first “water hardened” then ground to a granular form. It is also important to determine the response of tree species to ash application as not all species respond positively to ash. There is also the potential to apply wood ash to agricultural land as it has similar characteristics to agricultural lime.

Characterisation Based on initial characterisation undertaken, ash from the pulp and paper sector in New Zealand contains elements such as calcium, potassium and magnesium which are known to be beneficial to improving nutrient uptake in plants. However the levels of various elements and carbon contents vary considerably between sites so the recycling options available to each site may be different. There is the option of

5 Photos of ash handling from ReAsh International handbook (http://www.baltic-

ecoregion.eu/index.php?node_id=110.1&lang_id=1) and presentation by Thacker 2012.

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blending the ash with other materials, such as WWTP sludge to improve nutrient value for certain applications. Volume and logistics The pulp and paper sector produces around 55,000 wet tonnes of ash per year, this equates to approximately 46,000 dry tonnes of ash based on typical moisture contents. In terms of scale, 1.5 million tonnes of agricultural lime were applied in 2007 to pasture in New Zealand (Statistics NZ (2007)). This was a decrease from 2002 application levels and, with the increase in Dairy farming, is likely to be less than is applied annually in NZ now. The current cost for agricultural lime ranges between $20-$50/tonne depending on location. Thus wood ash from the Pulp sector may have benefits to agricultural areas around the mill site on a cost basis. The logistics of first treating then transporting the granulated ash is site specific and would need to be assessed on a case by case basis.

Access Application of ash to forestry may appear to be the easiest option for the pulp and paper sector as all of the ash-producing mills are near forests however, the uptake of wood ash for forest application will depend on getting buy-in from the forest growers. Pulp mills in NZ used to own and have control over their own forests however only one of the mills involved in this study currently owns significant areas of forest land. The other mills either have parent or completely separate companies that own the forest. Thus one of the barriers to uptake of ash application to forest land is access to the forests. Benefits of large-scale application of wood ash to land are not widely understood in NZ.

In some areas the forest terrain is also difficult to access for ash application. In these areas, application of ash to agricultural land may be a more suitable option if transport distances become a barrier. Application of wood ash to agricultural land likely would require involvement of the fertiliser industry and associated channels. These companies would be critical to creating a sustainable market and selling the benefits of wood ash application to agricultural land owners.

Implementation pathway The recycling of wood ash to land in NZ will depend on getting the right people informed of the fertiliser benefits. The ash volumes are not significant in the context of the current fertiliser industry and a number of pathways are possible from direct relationships with forest owners, to integration in established fertiliser manufacturing supply chains. There are two options for ash in this context. The first option is for

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treated ash to be applied directly to land. The second option is for ash to be blended with other beneficial products, such as commercial fertiliser or vermicompost that contain complementary characteristics for land improvement. Blending ash potentially allows for:

• reduced costs in terms of ash treatment • reduced disturbance of land by having one visit

to apply fertiliser • increased soil and plant health by providing a

tailored application Significant international experience and examples exist in the field of recycling wood ash. A Swedish demonstration project for Forest application of ash provides a good starting place for examples of what methods other organisations have used to get buy-in from forest growers (RecAsh 2010). This Swedish project has also produced an International Handbook “From extraction of forest fuels to ash recycling” which is available on-line (http://www.baltic-ecoregion.eu/index.php?node_id=110.1&lang_id=1). The proposed implementation pathway for this option is;

1. Direct engagement with fertiliser industry and potentially end-users such as forest growers to further define scope of opportunity;

2. Establish collaboration of interested parties including wood ash producers, fertiliser industry, and end users;

3. Identify options for demonstration sites to enable international experience on ash recycling to be tested in NZ;

4. Undertake ash recycling trials and education and outreach programmes to extend understanding of benefits to a wider audience of potential end-users.

Ash for construction/roading (aggregate/lime) The high calcium oxide concentration in wood ash from pulp mills means that it is a potential substitute for burnt lime in construction or roading materials. While there are numerous material pathways for substitution of ash into construction materials, many require strict quality parameters to be met depending on the source and end-use of the final product.

Characterisation The bottom ash from pulp mill boilers in NZ is high in calcium (6-146 g/kg), low in total carbon (0.07-5%) and has bulk densities ranging from 959 to 1300 kg/m3. Wood fly ash (Loss on ignition 21%; Ca 250 mg/kg) has been applied to forestry roads in the USA to reduce rutting created by logging trucks (Hoffman, M.K. 2003; Thacker 2012). Projects in Finland have also demonstrated that fly ash can be used to improve unpaved roads either on its own or in combination with

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WWTP residuals6. Austrian researchers (Supanic and Obernberger 2011) have also shown that bottom ash can be substituted for burnt lime (CaO) as a binding material for stabilisation of soil under paved roads. Butul (2000) found that wood ash could be used as a 10-15% replacement of cement in asphalt mixes without compromising the mechanical properties of the mix. The cost analysis that Butul carried out indicated a saving of 6% for ash replacement of 15%. Low carbon wood ash has the pozzolanic characteristics suitable for inclusion in cement but the international technical standards (Appendix A -Table 1A) for concrete are based on a specific material (coal ash) and therefore inhibit the uptake of wood ash for this application (Thacker 2012; Recycled resource recovery centre website).

Volume and logistics Boiler ash from the Pulp and Paper sector in NZ consists of approximately 30% bottom ash (~12000 tonnes/yr). This is a very small volume compared to the burnt lime currently used in NZ road construction so any application in this space would be locally based – either on local forestry roads or for small applications around site. Supanic and Obernberger (2011) noted that the bottom ash they investigated could not be spread using traditional spreaders so the application rate was twice as slow as applying lime.

Access The potential use of bottom ash from boilers on forestry roads is likely to be difficult due to the lack of experience and information on the use of bottom ash as a soil stabiliser. The NZ Forest Road Engineering Manual updated in 2012 has no reference to the use of wood ash as a stabiliser. Implementation pathway Uptake of wood ash for construction, in particular road construction in NZ would require involvement with a roading contractor that, depending on scale, could run trials to determine the efficacy of using pulp mill bottom ash in roading. While a number of niche applications of incorporating wood ash into construction materials exist overseas they are highly specific to their local context and can not necessarily be readily replicated. A proposed implantation pathway for further development of this option is;

1. Establish a regional inventory of quantity and key quality data for wood ash production;

2. Engage with construction material supply chains in the respective regions to identify specific opportunities to develop demonstration projects;

3. Extend successful demonstration projects to other regions.

6 Forestry road in Finland containing 30% wood ash and 70% gravel. Photo by Vanhanen et al.

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Wastewater Sludge Wastewater sludge is currently landfilled, vermicomposted or burnt at the various mill sites in NZ. In all cases there are advantages and disadvantages with the option employed and there is a need to have a clear understanding of the costs and benefits of each option and its value across the sector (Mahmood, T. and A. Elliot 2006; Slade, A. et al. 2006). Landfill is low risk from a security perspective but carries the cost of engineered air space now and into the future. Vermicomposting is low cost but requires a considerable land area and relies on a credible operator with secure markets to represent a long term option with an acceptable risk profile. Burning has implications for boiler operations and needs to be considered in light of the overall fuel mix available for a specific site. Having a range of options available makes sense in many cases and in some cases the approach adopted for the management of sludge has the potential to be relevant for other organic waste streams in the surrounding area e.g. vermicomposting of putrescible organic wastes, burning of dry biofuel (sawdust, bark). Sludge vermicomposting7 Vermicompost is the product or process of composting using compost worms to create a heterogeneous mixture of decomposing vegetable or food waste, bedding materials, and vermicast. The material used for vermicomposting needs to be presented as a blended mass at an acceptable carbon to nutrient ratio. If the ratio is too high or too low, waste degradation is slowed. Vermicompost can be used as a soil conditioner or as a fertiliser, depending on the starting biomass. Plant growth trials have shown that small amounts of vermicast added to soil or potting mix can increase the growth of plants and trees. Vermicast, also called worm castings, worm humus or worm manure, is the end-product of the breakdown of organic matter by an earthworm. These castings have been shown to contain reduced levels of contaminants and a higher saturation of nutrients than do organic materials before vermicomposting (Negi and Suthar 2013). Due to the lower composting temperature, vermicasts have higher microbial loading than conventional composting and generally have reduced levels of pathogens such as E Coli but can show increases in other microorganisms due to spore germination in the worm gut (Eastman et al. 2001, Negi and Suthar 2013).

Industrial-scale vermicomposting is increasing around the world as is the science relating to vermicomposting (Yadav and Garg 2011, Negi and Suthar 2013).

7 Photo of vermicomposting pulp mill WWTP residuals courtesy of Michael Quintern (My Noke) (2013).

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Characterisation Pulp and paper derived vermicompost has low nutrient value but can be used as a soil conditioner. The biological sludge contains 2-3% nitrogen compared with 0.1% for the primary solids. Pulp and paper waste solids can be combined with other high nutrient waste sources, such as municipal biosolids, to produce a soil fertiliser. Volume and logistics The pulp and paper sector collectively produce 179,000 wet tonnes per year of wastewater treatment solids. Vermicomposting operations require storage onsite for up to 9 months to complete the process, depending on the vermicomposting design. For example, high capital systems with more handling involved can vermicompost for a shorter time than less capital intensive windrow systems. The land area required for windrowing this scale of vermicomposting is significant and the size of the market required to support this scale has not been fully developed in NZ. Potential for odour generation is an issue for mill sites with close neighbours. Access Vermicomposting specialist, MyNoke has obtained organic certification for vermicompost derived from 100% pulp and paper WWTP sludge in NZ. This certification provides some level of access to farms that practice organic farming. However the benefits of large scale application of vermicompost to agricultural land in NZ are not widely known so the market is small at present. With increased understanding and scale of supply this market may grow, particularly in drought prone areas where increased carbon content in the soil can increase the water holding capacity. Implementation Pathway This technology is already underway in NZ but the long term market capacity for 100% of Pulp and Paper WWTP sludge to be processed by this technology has not been determined. The sector is keen that the market capacity or readiness for vermicompost is assessed for NZ before expanding operations any further. A proposed implementation pathway for further development of this option is:

1. Perform a market analysis and supply chain assessment for pulp and paper sector vermicompost in NZ.

2. If the option has significant market capacity the next stage would be to assess the capability of the current operators to sustainably handle operations of this scale.

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Sludge land spreading Land spreading is the application of dried, dewatered or semi-treated pulp and paper waste solids to forestry or agricultural land for soil enhancement. Land spreading of solid waste from pulp and paper (and municipal) is common around the world, either partially composted or mixed with other wastes.

Characterisation Land spreading is a beneficial re-use of pulp mill derived waste solids. It enhances soil quality by increasing its organic content, thereby increasing biological activity, fertility and structure (Camberato et al. 2006) as long as the receiving soil is not:

• an organic soil • a soil with C:N ratio greater than 40:1 • a soil which has an EC (electrical conductivity) great than 6 dS/m • a soil which has a SAR great than 8 • a soil in low lying areas that has saturated soil conditions for more than six

consecutive weeks.

These are the requirements outlined in the standards and guidelines for the land application of mechanical pulp mill sludge to agricultural land (Alberta Environmental Protection Environmental Sciences Division (1999)). The resulting soils also show increased infiltration of rain and moisture retention, which could be of particular use in drought regions. Further positives can include; liming benefits, improved nutrient supply, and decreased soil erosion as the solids help hold the soil. High rate application of waste solids reduces weed germination, emergence and growth. Land spread solids have a high carbon: nitrogen ratio so can be blended with high N wastes (such as municipal waste solids). Laboratory studies show the benefits of land spreading to be; increased germination rates, more root development, and a greater capacity to hold moisture in the sludge-amended soil than in the controls. Land spreading could be used to return eroded sites to productive use, turn forestry land into farm land, and restore the lands aesthetic appearance. Land spreading removes the need for the sludge to be landfilled or combusted. Volume and Logistics Sludge can be added either wet or dried/dewatered, as a liquid, slurry, dewatered cake, or as dried pellets. Dried solids can be more easily and cost effectively transported - to sites further from the mill. Wet solids can be spray applied, but transportation costs are high. Dried solids can be spread directly or watered down to spray apply.

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Simple land-spreading of sludge is a much cheaper option than either composting or vermicomposting, however consideration needs to be given to the nutrient ratios present in the waste solids and the ratios required by the local soil types. Access Land spreading of municipal biosolids already occurs in NZ however access to suitable land is an issue. In most cases pulp mill solids and sludges are not contaminated or hazardous (heavy metals, chlorinated organics etc) (Fraser, D.S. 2007). Despite this its use is greatly affected from perceived and/or real concerns, which control where it is possible to land spread and long term market security. This option is suitable for pulp mills with access to their own land. It is less likely that this option will be taken up by agricultural land owner as areas spread with sludge need to be left fallow for a period of time before stock is allowed access or planting occurs. Implementation Pathway This technology is already underway in NZ but the long term market sustainability has not been determined. A proposed implementation pathway for further development of this option is:

1. Perform a market access and sustainability analysis and supply chain assessment for pulp and paper sector in NZ.

2. If the option has significant market capacity, connect mills with experienced and reputable operators.

Sludge burning Combustion of sludge involves the total conversion of organic solids to oxidised end products, primarily carbon dioxide, water and ash. Combustion provides substantial waste reduction and recovery of energy in the form of heat and steam. Pulp mills in NZ have existing energy boilers of various types and ages, which take a mixture of wood waste and other fuels. In some cases dewatered sludge is fed to the boiler but the net energy content able to be realised depends on the water content. Other fuel sources wood residues and waste oil may exist on site but use of these depends on consent conditions and ease of integration with existing fuel feed mechanisms. Discharges (emissions to air and ash) from the boilers depend on fuel inputs and combustion control. Monitoring for NOx, SOx, VOCs and particulates may be required and regular maintenance to reduce the build-up of corrosive or scaling materials will be necessary.

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Characteristics For sludge to be burnt effectively in a modern boiler, the solids content should be greater than 25% (Figure 3). It is also beneficial if the sludge does not contain high levels of corrosive elements such as chlorine. The biological sludge is typically only 22-27% solids whereas the primary sludge, which is mostly fibre for the mechanical mills can reach 34-45% solids. Figure 3 Fuel triangle for waste from the paper industry (blue spot=deinking pulp mill sludge. The red area is the optimum area for fuel for a standard boiler (Likon and Trebše 2012). Two of the pulp mills involved in this project, currently burn sludge in their boilers. One site has a fluidised bed boiler which is designed to burn biomass with high moisture content. Volume and logistics The two mills currently burning sludge are able to dispose of 100% of their sludge by this method while maintaining the energy requirements for their mill. The impact of burning high moisture content sludge is a reduced boiler heat output which may impact on site process heat supply if enough dry supplementary biomass fuel cannot be sourced or the boiler is at capacity. According to Kraft and Orender (1993), for each additional 1% of moisture content in sludge, the temperature of combustion must increase another 10°C to maintain process efficiency. Proximity of the WWTPs to boiler systems and different methods for collecting sludge will also have a potential impact on the viability of burning. Access All of the mills have biomass boilers but not all of the boilers are suitable for burning high moisture content WWTP sludges. The primary solids from Kraft pulp mills also have high ash content due to the lime mud and other inorganics collected from the process.

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Implementation Pathway Sludge burning is a viable current option for landfill diversion and has been implemented by two of the mills in NZ. However, maintaining solids contents of great than 25% are difficult particularly in winter. Improvements in either fuel storage or sludge drying/dewatering will improve energy recovery potential (Green, D.L et al. 1991; Drogui,Pet al. 2002). Increased solids content should improve fuel value and reduce ash production. However it is important to note that if the sludge is too dry and light-weight it may not be compatible with certain boiler designs.

A proposed implementation pathway for further development of this option is:

1. Assess the potential for reduction of sludge to landfill at the mills not currently burning sludge.

2. Work with the mills currently burning sludge to reduce the sludge moisture content below 75% on a consistent basis.

Sludge anaerobic digestion Anaerobic digestion is biological process in which microorganisms break down biodegradable material in the absence of oxygen. It can be used for industrial or domestic purposes to reduce waste and/or to release energy (Metcalf & Eddie 2003; Gavrilescu, D. 2008).

The infrastructure required for anaerobic digestion at industrial scale can either involve construction of high rate, tank based digestion systems or simple covered pond systems. Solids reduction in the order of 50-65% can be achieved through high-rate anaerobic digestion systems and the

final sludge is easier to dewater than sludge from aerated treatment systems (Metcalf & Eddie 2003). It is often used to treat high strength wastewaters and sewage sludge, in an integrated waste management system. The digesters can also be fed with purpose-grown energy crops, such as maize to boost biogas recovery rates. The nutrient-rich digestate produced can be used as fertilizer. The biogas (methane and CO2) produced by anaerobic digestion can be used to generate heat and/or power.

Characterisation The key challenge for pulp mill waste is the potential inhibitory effect of extractives and lignin in the case of mechanical mills. These compounds can be reduced by removal prior to anaerobic treatment either by aerobic treatment; flocculation or selective removal for other uses. The two mechanical mills do remove extracts in the process DAF (dissolved air flotation) units. This flocculated solid is dewatered and burnt in the boiler.

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The biological sludges from the pulp mill activated sludge plant does have a suitable C:N ratio for effective anaerobic digestion. The optimum C:N ratio ranges from 20:1 to 30:1. However the primary sludge is very low in nitrogen as it is mostly wood fibre. Addition of higher nitrogen feedstocks may be required to achieve reasonable yields of methane for energy if biological and primary sludges were to be digested anaerobically and sludge pretreatment may be required to improve digestability (Elliot and Mahmood 2007; Hagelqvist, A. 2013 a & b). Volume and logistics Anaerobic treatment plants can be low or high tech depending on mill requirements, sludge volumes and footprint constraints. The volume of WWTP biological sludges at each site is sufficient to run an anaerobic digester system however if primary and biological sludges were to be combined for anaerobic digestion there would need to be a consistent supply of an amendment material that contains high nitrogen. Access Access is not an issue for the generic technology, however capital cost and payback is likely to be an issue if anaerobic digestion tanks are the preferred option, rather than covered ponds. Anaerobic digestion in tanks is a relatively high capital process to implement. Anaerobic digestion has also not been tested in NZ for pulp mill biological sludges. The economics may be further improved by considering that ammonia released during the anaerobic process could be used to offset considerable nutrient costs in the existing mill wastewater treatment systems. Implementation This option requires full scoping to assess the real benefits and potential payback. The technology implementation risk is substantial in its current form with very little direct experience on pulp mill wastes overseas may be reduced by medium-scale anaerobic digestion trials. If the value proposition is compelling enough for a site, de-risking is likely to be required though a pilot development program. A proposed implantation pathway for further development of this option is;

1. Undertake a more detailed scoping study of anaerobic digestion opportunity for a site with an interest in further development;

2. Engagement of a suitably experienced technology partner; 3. Development of a pilot scale demonstration project for long term trial

operation; 4. Validation of full-scale value proposition; 5. Dissemination of business case benefits for broader application and uptake.

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Summary Site and sector level workshops backed with data summaries for all sites resulted in valuable discussions relating to technology options that best suited the different sites. The wastewater treatment systems at each pulp processing site provide different constraints on sludge management when assessed against the sludge technology options. For some sites improved sludge dewatering is a primary concern at present, whereas for other sites the concern is with security of current diversion options for sludge. The other common solid waste that all mills, other than the 100% recycle mill, have is boiler ash. These mills use their wood and bark waste to create energy but in turn produce significant quantities of ash. From the evaluation process to date, this waste provides the best opportunity for a sector wide and potentially national level initiative as biomass boilers are increasing in New Zealand. The fourth phase of this project will use the outcomes of this report to provide a National level strategy for reducing pulp and paper sector solid waste to landfill.

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References Alberta Environmental Protection Environmental Sciences Division (1999) Standards and guidelines for the land application of mechanical pulp mill sludge to agricultural land. http://environment.gov.ab.ca/info/library/7267.pdf Bird, M.; Talberth, J. (2008) Waste stream reduction and re-use in the pulp and paper sector. Washington State Department of Ecology – Industrial Footprint project. www.sustainable-economy.org.

Butul, B (2000) Performance characteristics of coal fly ash and wood ash-modified asphalt binder. Masters Abstracts International, Volume: 38-06, page: 1648. Florida Atlantic University. Camberato, J.J.; B. Gagnon; D.A. Angers; M.H. Chantigny and W.L. Pan (2006) “Pulp and paper mill by-products as soil amendments and plant nutrient sources.” Canadian Journal of Soil Science 86(4): 641-653. Cavaleri, M.A.; Gilmore, D.W.; Mozaffari, M.; Rosen, C.J.; Halbach, T.R. (2004). Hydrid poplar and forest soil response to municipal and industrial by-products. J. Environ. Quality 33(3): 1055-1061. Drogui,P.; J.F. Blais and G. Mercier (2002) “Pilot plant study for enhancing dewaterability and stabilizing wastewater sludge from paper mill industries.” INRS-Eau Terre et Environnement, Canada Report. Accessed at www.bvsde.paho.org/bvsaar/cdlodos/pdf/pilotplant311.pdf . Eastman, B.R.; Kane, P.N.; Edwards, C.A.; Trytek, L.; Gunadi, B.; Stermer, A.L.; Mobley, J.R.(2001) The effectiveness of vermiculture in human pathogen reduction for USEPA biosolids stabilization. Compost Science & Utilization 9(1):38-49. Elliot, A. and Mahmood, T. (2006) Beneficial uses of pulp and paper power boiler ash residues. Tappi Journal 5(10): 9-16. Elliot, A. and Mahmood, T. (2007) Pretreatment technologies for advancing anaerobic digestion of pulp and paper biotreatment residues. Water Research 41: 4273-4286. Fraser, D.S. (2007) “Fate and effects of pulp mill effluent solids in the soil environment.” PhD Thesis. Waikato University, NZ. pp1-187. Gavrilescu, D. (2008) “Energy from biomass in pulp and paper mills.” Environmental Engineering and Management Journal 7(5): 537-546. Green, D.L.; W.L. Root and R.J. Fortier (1991) “Turning biological waste treatment sludge into a fuel source.” Proceedings of the Water Pollution Control Federation’s 64th Annual Conference, Toronto. pp1-20. Hagelqvist, A. (2013a) “Sludge from pulp and paper mills for biogas production. Strategies to improve energy performance in wastewater treatment and sludge management.” Thesis from the Faculty of Health, Science and Technology, Karlstad University. pp1-46. Hagelqvist, A. (2013b) Batchwise mesophilic co-digestion of secondary sludge from pulp and paper industry and municipal sludge. Waste Management 33: 820-824.

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Hoffman, M.K. (2003) “Beneficial reuse of boiler ash at Savannah River Mill, Georgia Pacific Corporation.” Proceedings of the Tappi International Environmental Conference. Jacobson, S. (2003) Addition of stabilized wood ashes to Swedish coniferous stands on mineral soils – effects on stem growth and needle nutrient concentrations. Silva Fennica 37(4): 437-450. Kraft, D.L. and Orender, H.C. (1993) Considerations for using sludge as a fuel. Tappi 76(3): 175-183. Likon M. and Trebše, P. (2012) Recent advances in paper mill sludge management. Chapter in Industrial Waste. Edited by Prof. Kuan-Yeow Show. Mahmood, T. and A. Elliot (2006) A review of secondary sludge reduction technologies for the pulp and paper industry. Water Research 40(11): 2093-2112. Metcalf & Eddy (2003). Treatment, Reuse and disposal of solids and biosolids. Chapter 14 in the 4th edition of Wastewater Engineering, Treatment & Reuse. p1514. Monte, M.C.; Fuente, E.; Blanco, A.; Negro, C. (2009) Waste management from pulp and paper production in the European Union. http://eprints.ucm.es/11900/1/Waste_management_M_C_Monte_2009.pdf Negi, R. and Suthar, S. (2013) Vermistabilization of paper mill wastewater sludge using Eisenia fetida. Bioresource Technology 128: 193-198. New Zealand Forest Road Engineering Manual (2012) www.nzfoa.org.nz/file...a.../484-nz-forest-road-engineering-manual-2012 Pitman, R.M. (2006) Wood ash use in forestry – a review of the environmental impacts. Forestry Advance Access.doi:10.1093/forestry/cp1041. pp1-26. RecAsh (2010) Regular recycling of wood ash to prevent waste production. RecAsh – A life-environment demonstration project. ec.europa.eu/environment/life/project/Projects/index.cfm? Recycled materials resource centre. Coal fly ash. http://rmrc.wisc.edu/coal-fly-ash/ Thacker, B. (2012) Road-related applications of paper industry byproducts. http://www.trb-adc60.org/downloads/Thacker%20ADC60%20Madison%202012.pdf Slade, A.; Wang H. and Dare P. (2006) Treatment technologies for primary and secondary wastewater solids: An overview. Scion Report Statistics NZ most recent Agriculture Census (2007). Supanic, K.; Obernberger, I. (2011) Wood ash utilisation as a stabiliser in road construction – first results of large-scale tests. http://www.bios-bioenergy.at/uploads/media/Paper-Supancic-Ash-Utilizationin-Road-Construction-2011-06-06.pdf Vance, E.D. (1997) Rercycling paper mill by-products on forest land: By-product composition, potential applications and industry case studies. Chapter 30 from “The Forest Alternative. Principles and practice of residuals use”. Editors: C.L. Henry; R.B. Harrison; R.K. Bastian. http://criticalpracticesllc.com/clh/FASProceedings/Ch30Vance.pdf

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Vanhanen, H.; Dahl, O.; Joensuu S. (2013) Utilization of wood ash as a road construction material – sustainable use of wood ashes. Proceedings of the 2nd International conference on Final Sinks: Sinks a vital element of modern waste management (16-18 May; Espoo, Finland). Yadav, A. and Garg, V.K. (2011) Industrial wastes and sludges management by vermicomposting. Rev. Environ. Sci. Biotechnol. 10:243-276.

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Appendix A Table A1 International specifications that apply to reuse of fly ash. (Recycled Resource recovery centre website http://rmrc.wisc.edu/coal-fly-ash/)

Specification Title Application

ASTM D242-04 Mineral Filler for Bituminous Paving Mixtures Asphaltic concrete

AASHTO M 172 Mineral Filler for Bituminous Paving Mixtures Asphaltic concrete

ASTM C593-06 Fly Ash and Other Pozzolans for Use with Lime> Soil stabilization

ASTM D 5239-04 Practice for Characterizing Fly Ash for Use in Soil Stabilization Soil stabilization

ASTM E2277-03 Guide for Design and Construction of Coal Ash Structural Fills Structural fill

ACI 232.2R Use of Fly Ash in Concrete Portland cement concrete

ASTM C311-05 Sampling and Testing Fly Ash or Natural Pozzolans in for Use in Portland-Cement Concrete

Portland cement concrete

AASHTO M 295 ASTM C618

Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in

Concrete

Portland cement concrete

ASTM C6103-04 Test Method for Flow Consistency of Controlled Low Strength Material (CLSM) Flowable fill

ACI 229R Controlled Low Strength Materials (CLSM) Flowable fill

ASTM D6024-02 Ball Drop on Controlled Low Strength Material to Determine Suitability for Load Application Flowable Fill

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Table A2 Evaluation of ash diversion technology options

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Table A3 Evaluation of sludge diversion technology options