24
Compost: The Ultimate in Recycling
Returns organic nutrients back to the soil for increased plant productivity Increases water retention in soil for drought resistance Long term sequestration of carbon, our best hope to combat climate change
The Science of Composting • Mesophilic Phase 1 (10-400 C)
• Lasts only a few days • Rapid growth of bacteria and fungi • Breakdown of soluble sugar and starches
•Thermophilic Phase (>400 C) • Mixed population of heat loving organisms • High heat helps breakdown of proteins, fats, “tough” plant material
like cellulose • High temperature (>55 0C) kill weeds and pathogen harmful to
humans • CO2 given off in large amounts
•Mesophilic Phase 2 (10-400 C) “Curing Phase” • Can last several months • Bacteria, fungi, actinomycetes predominate. Invertebrates active. • Supply of organic material has decreased. Slow breakdown of
cellulose and lignins. Humic compounds form. • Mineralization of Nitrogen
Microbes break down organic nutrients into plant accessible forms
1. Bacteria: major decomposers, breakdown many forms of organic material such as proteins, cellulose and lignin
2. Archaea: Able to withstand high temperatures. Generation of methane and oxidation of ammonia to nitrite
3. Fungi: Break down tough debris, too dry, too acidic or too low in nitrogen for bacteria to digest
Compost as Soil Amendment
Soil Organic Mater (Compost) as a supplier of nitrogen, phosphorus and sulfur nutrients to plants
How do soil amendments, such as compost, work?
Multiple, Interdependent Microbes are Responsible for the Action of Compost in Soil
To develop a more predictive understanding of the mechanism of compost amendment on increased beneficial soil activities we must understand the role of the microbes in the process!
Microbes involved in: Organic matter decomposition Nitrogen Cycle Phosphorus Cycle Sulfur Cycle Carbon Cycle Humus Production and increased CEC
- -
- -
The Nitrogen Cycle Microbes convert nitrogen to many different forms
Decomposition: Organic Biomass to Ammonia (NH4) Bacteria, fungi and actinobacteria
-Nitrification: NO2
Nitrosomonas (Aerobic) NO2 NO3
Nitrobacter
Oxidation of Ammonia to Nitrite NH4
Dentrification: Heterotrophic Nitrate Reduction NO3 NO2
Paracoccus denitrificans -(Anaerobic) NO2 NO + N2O N2
Figure 4: Effects of social regulation on microbial organic matter decomposition.
From: Social dynamics within decomposer communities lead to nitrogen retention and organic matter build-up in
soils
a Without social regulation
All microbes make extracellular enzymes
Loss of labile C and N
Fast decay Large DOM flow
Dead plant matter (N-poor)
Jft\ Enzymes
I
b With social regulation
Only a fraction of microbes make extracellular enzymes
Enzyme producer
Cheater
~/ooM DOM
/ Slow decay Small DOM flow
•• --Community regulation: the higher the enzymatic capacity per producer, the more cheaters will be present
Relatively more N in DOM because of larger contribution of microbial necromass
Additional accumulation of microbial remains due to lower enzymes:microbial biomass ratio
Large accumulation of total organic matter due to fewer enyzmes overall
From: C. Kaiser et al. Nature Communications 1 December 2015
-E Q. Q. -C 0 -a, a.. -C G) u C 0
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Full Record ending October 9, .2016
Annual C.ycfo
350 -
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1960 196S 1970 11975 1980 1985 1990 1995 2000 2005 2010 2015
The Keeling Curve: A daily record of atmospheric CO2
Nicasio Composting Facility for Microbe Characterization
What are the microbes doing in the compost environment?
Experimental procedures
• Hourly monitoring of temperature (center and edges), oxygen and moisture
• Periodic sampling for microbial DNA, carbon/nitrogen, greenhouse gases (CH4, N2O, CO2)
• PhyloChip characterization of microbial communities throughout process
• Standard biosolids indicators (Salmonella, Fecal Coliforms, Helminth ova ) before and after treatment
• • • • • • • • • •
•••••••••••••••••
•••• •••• ••••••
The Berkeley PhyloChip
comprehensive microbial census
•1.1 million DNA probes to detect > 50,000 bacteria and archaea in a single test
Hierarchical probes for identification at multiple taxonomic levels
Rapid, repeatable and standardized method with statistical confidence
Comprehensive identification of entire microbial community to monitor changes in environment.
160 Fate of fecal bacteria in thermopile
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Improving Sanitation in Haiti • Conventional sewage treatment expensive to build and
operate
• Requires high volumes of increasingly scarce and expensive water, chemicals and energy
• Conventional treatment systems often impractical -impoverished regions, remote places, disaster areas
Compost from human waste in Haiti
Providing sustainable sanitation solutions
Compost and Soil Nutrient Availability
DNA Everywhere Project Goal- Develop simplified methods for DNA extraction and train individuals where infrastructure does not currently exist
Fate of fecal bacteria during thermophilic
0
500
1000
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2000
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3500 Cap-Haitien Port-au-Prince
Average number of bacterial types per compost process stage
composting of human waste in Haiti
Cap-Haitien Port au Prince
Observed significant reduction in human fecal
organisms throughout the process Bucket Thermophilic Cured/Bagged
Cap
-Hai
tien
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Pri
nce
One time application of compost to grasslands
Prof. Whendee Silver – UC Berkeley
• Spread 1 cm compost on surface of California grasslands • Identified a significant increase in plant productivity, water
retention and carbon storage (2 tonnes/hectare) • Next 5 years - additional 2 tonnes per year in stable, microbial
resistant carbon. Model predicts additional 30+ years. • UNKNOWN: what are the microbial mechanisms for C, N, PO4
cycling, humus production and contaminant degradation?
mmonl o t11lutlon
2
Nitrogen Conversion and Emission During the Composting Process
From: K. Maeda et al. Microbial Biotechnology (2011) 4:700-9
Ongoing and future research at Berkeley Lab
• Increasing Available Feedstock for Compost Production The fate of pharmaceuticals in compost. Optimization of the thermophilic composting process for
enhanced pathogen and VOC emission reduction – biosolids, dairy, septic alternative.
• Compost Application for Greenhouse Gas Reduction Microbial mechanisms for long-term soil carbon sequestration. Life cycle analysis for best use of potential feedstocks.
• Healthy Soils Through Compost Amendment Functional analysis of nitrogen-, carbon-, phosphorus-, sulfur-
cycle. Diagnostics for healthy soil. Microbial mechanism for increased soil water holding capacity. How does the starting compost material (food waste, CAFO,
biosolid, green bin, etc.) impact long-term plant productivity? -
