Bioenergy FundamentalsBiomass – solar energy stored in plant/animal

tissueChemical Composition

25% Lignin75% Carbohydrates and Sugars

Carbohydrate – many sugars bound together into long polymer chains

Carbohydrates consist of cellulose/hemicelluloseLignin – a non-sugar polymer, like plant mortar

- Glue that holds cellulose fibers together

Lignin Molecular Structure

Carbohydrate/Cellulose Structure

Origins of Biomass

CO2 + H2O + Sunlight = Biomass + O2

Solar Radiation Chemical EnergyCyclic Process14% of worldwide energy consumption40-90% in developing world4% of U.S. electricity from biomass (9000 MW)Mass of total living matter = 2000 billion tons

or 300 tons per personNet Annual Production = 400,000 million tons

Energy Content of Biomass

Moisture content causes huge variation8-20% for wheat straw30-60% for wood75-90% for animal manure

Dry biomass - 17-20 GJ/ton (coal 20-30 GJ/ton)Biomass – less ash, toxic metals, sulfur, etc.Wide range of usesCyclic process that is potentially sustainable

Common Pathways

Developed, Widespread UseFirst Generation Biofuels – Ethanol,

BiodieselLandfill and Digester GasesIndustrial and Agricultural Wastes

(Sawmills…)

Future DevelopmentSecond Generation Biofuels – Range of feedstocks, conversion

processesAdvanced use of residential, industrial and

agricultural wastes, byproducts and crops

Ethanol

EthanolSubstitute for GasolineProduced by fermenting sugar cane or sugar beetProduced in large quantities in BrazilCan also be made from vegetable starches –

requires milling and treatment with acidsEnergy content = 30 GJ/tonEnergy content about 2/3 that of gasoline

C2H5OH

Ethanol

So, you pull up to the gas station in your flexible fuel vehicle and see that gasoline is selling for $3.00 per gallon and ethanol (100%) is selling for $2.12 per gallon. Which is a better deal?

Ethanol

Commonly blended with gasolineUp to 10% ethanol with gas, octane boost85% ethanol + 15% gasoline = E85

Octane rating – what is it…Octane rating of ethanol about 1135-10% blends boost octane rating 2-4 pointsBefore ethanol was used, MTBE

Ethanol

Methyl tert-butyl ether, C5H12OPollutes groundwater

- leaks from storage- leaks from fueling- leaks from industry

Also used as oxygenate- Winter fuel blends- Reduces CO emissions

Ethanol

Ethanol1. Corn stored at plant (7-10 day supply)2. Screened to remove debris, milled into flour3. Liquefaction (aka. Mashing)• Hot slurry (mixed with water, enzyme

added, heated for 30-45 minutes)• Time, heat and enzymes break down starch

into shorter chains4. Saccharification – Glucoamylase enzyme

breaks short chains into simple sugars5. Fermentation – Yeast converts sugar into

ethanol, 50-60 hours to 15% alcohol “beer”

Ethanol6. Distillation – Difference in boiling point of

alcohol and water, produces 95% alcohol7. Dehydration – Remaining water from 190

proof alcohol removed through molecular sieve (uses different sizes of molecules)

Byproducts- CO2 from fermentation- Spent grains – turned into cattle feed

Biodiesel

Diesel fuel from vegetable oil (or animal fat)Veg oils – fatty acids (triglycerides)Long chain alkyl (methyl, propyl, ethyl) estersAn ester group…

Glycerol

O O OMe Me Me

O = O =O =

HO

HO

HO

Biodiesel(Methyl Ester Alcohol)

3 ester alcohol + 1 glycerine

O =O O

O =O

O =

Triglyceride

1 triglyceride + 3 alcohol

3 MeOH

KOHCatalyst

catalyst

Transesterification Reaction

PROF. NAVEEN KUMAR, DELHI COLLEGE OF ENGINEERING, DELHI, INDIA

Fats and oils have quite big molecules with a spinal of glycerol on which are bond three fatty acid rests.

By the transesterification, the fatty acid rests are removed from the glycerol and each is bond with methanol.

The products are one mole glycerol and three mole of fatty acid methyl ester.

Molecular Structure

Biodiesel

Biodiesel

For every ton of biodiesel, 100 kg of glycerol Market for glycerol used to exist… not anymore

(everybody is making biodiesel)Companies are trying to find ways to use it

(Cargil, Dow, etc.)High water content, not cheap to separate

Market for free/cheap veg oil used to exist…(but everybody is making biodisel)

Biodiesel

What the ?!!?!?!

BiodieselSources

- Palm (41 million tons per year)- Soybean (38 million tons per year)- Rapeseed (aka Canola, 18 mil. tons per

year)- Sunflower, peanut, cottonseed, olive, etc.

Can be run 100% or any blendVolumetric heating value 10% less than dieselWater emulsifications a serious problem

Pyrolysis

Decomposition of solids- High temperatures- Absence of oxygen

Pyrolysis of biomass- Heated to 400-500oC for a few seconds- Yields a bio-oil- Not a fuel that can be burned directly

Currently in commercialization phase

Catalytic Reforming

Biogas transformed into liquid fuelTypically a CO and H2 blend to produce gasoline

or diesel substituteKey component is the catalyst

Transition metals (iron, cobalt, ruthenium)Most common method is called Fischer-Tropsch

Short course in catalysis…

Technical Skills for Liquid Biofuels

Combustion- Stoichiometry (proper A/F ratio, etc)- Heating value of a fuel or mixture (by vol)- Product gas composition- Assessing pollutant, GHG emissions

Otto, Diesel Cycle FundamentalsLife Cycle Analysis

- Quantification of energy, GHG, emissions- Does it make sense to do this?- Where should we focus to improve

process?

Stoichiometry Example

Calculate the following information for an E85 fuel assuming that the 15% is composed of C8H18

• Stoichiometric A/F Ratio• Lower heating value of the fuel in kJ/kg and

kJ/gallon• Mass of CO2 produced per kg of fuel burned• Mass of CO2 produced per MJ of energy

released