Bioenergy Fundamentals Biomass – solar energy stored in plant/animal tissue Chemical Composition 25% Lignin 75% Carbohydrates and Sugars Carbohydrate – many sugars bound together into long polymer chains Carbohydrates consist of cellulose/hemicellulose Lignin – a non-sugar polymer, like plant mortar - Glue that holds cellulose fibers together

Lignin Molecular Structure

Carbohydrate/Cellulose Structure

Origins of Biomass CO 2 + H 2 O + Sunlight = Biomass + O 2 Solar Radiation  Chemical Energy Cyclic Process 14% of worldwide energy consumption 40-90% in developing world 4% of U.S. electricity from biomass (9000 MW) Mass of total living matter = 2000 billion tons or 300 tons per person Net Annual Production = 400,000 million tons

Energy Content of Biomass Moisture content causes huge variation 8-20% for wheat straw 30-60% for wood 75-90% for animal manure Dry biomass GJ/ton (coal GJ/ton) Biomass – less ash, toxic metals, sulfur, etc. Wide range of uses Cyclic process that is potentially sustainable

Common Pathways Developed, Widespread Use First Generation Biofuels – Ethanol, Biodiesel Landfill and Digester Gases Industrial and Agricultural Wastes (Sawmills…) Future Development Second Generation Biofuels – Range of feedstocks, conversion processes Advanced use of residential, industrial and agricultural wastes, byproducts and crops

Ethanol

Substitute for Gasoline Produced by fermenting sugar cane or sugar beet Produced in large quantities in Brazil Can also be made from vegetable starches – requires milling and treatment with acids Energy content = 30 GJ/ton Energy content about 2/3 that of gasoline C 2 H 5 OH

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 gasoline Up to 10% ethanol with gas, octane boost 85% ethanol + 15% gasoline = E85 Octane rating – what is it… Octane rating of ethanol about % blends boost octane rating 2-4 points Before ethanol was used, MTBE

Ethanol Methyl tert-butyl ether, C 5 H 12 O Pollutes groundwater - leaks from storage - leaks from fueling - leaks from industry Also used as oxygenate - Winter fuel blends - Reduces CO emissions

Ethanol

1.Corn stored at plant (7-10 day supply) 2.Screened to remove debris, milled into flour 3.Liquefaction (aka. Mashing) Hot slurry (mixed with water, enzyme added, heated for minutes) Time, heat and enzymes break down starch into shorter chains 4.Saccharification – Glucoamylase enzyme breaks short chains into simple sugars 5.Fermentation – Yeast converts sugar into ethanol, hours to 15% alcohol “beer”

Ethanol 6.Distillation – Difference in boiling point of alcohol and water, produces 95% alcohol 7.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) esters An ester group…

Glycerol OOO Me O = HO Biodiesel (Methyl Ester Alcohol) 3 ester alcohol + 1 glycerine O = OO O Triglyceride 1 triglyceride + 3 alcohol 3 MeOH KOH Catalyst 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

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 ?!!?!?!

Biodiesel Sources - 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 blend Volumetric heating value 10% less than diesel Water emulsifications a serious problem

Pyrolysis Decomposition of solids - High temperatures - Absence of oxygen Pyrolysis of biomass - Heated to o C 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 fuel Typically a CO and H 2 blend to produce gasoline or diesel substitute Key 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 Fundamentals Life 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 C 8 H 18 Stoichiometric A/F Ratio Lower heating value of the fuel in kJ/kg and kJ/gallon Mass of CO 2 produced per kg of fuel burned Mass of CO 2 produced per MJ of energy released