Chip Chat: Oct 2017 Solar-energy driven bioethanol production

Biofuels Fuel that is produced through contemporary biological processes Biofuels currently in use Bioethanol (corn, cellulose, sugarcane) Biodiesel (from rapeseed and soybeans) Others: Bioethers, Syngas, Solid biomass fuels

Lifecycle: Bioethanol versus Petrol

Bioethanol Production

Bioethanol production Feedstock Supply: Feedstocks for biochemical processes are selected for optimum composition, quality, and size. Feedstock handling systems tailored to biochemical processing are essential to cost-effective, high-yield operations. B. Pretreatment: Biomass is heated (often combined with an acid or base) to break the tough, fibrous cell walls down and make the cellulose and hemicellulose easier to hydrolyze (see next step). C. Hydrolysis: Enzymes (or other catalysts) enable the sugars within cellulose and hemicellulose in the pretreated material to be separated and released over a period of several days. D1. Biological Conversion: Microorganisms are added, which then use the sugars to generate other molecules suitable for use as fuels or building-block chemicals. D2. Chemical Conversion: Alternatively, the sugars can be converted to fuels or an entire suite of other useful products using chemical catalysis. E. Product Recovery: Products are separated from water, solvents, and any residual solids. F. Product Distribution: Fuels are transported to blending facilities, while other products and intermediates may be sent to traditional refineries or processing facilities for use in a diverse slate of consumer products. G. Heat & Power: The remaining solids are composed primarily of lignin, which can be burned for heat and power.

Principle of fermentation Summarizing chemical equation for ethanol fermentation: C6H12O6 → 2 C2H5OH + 2 CO2 One glucose molecule is converted into two ethanol molecules and two carbondioxide molecules.

Bioethanol Feedstocks

First/Second generation First generation versus second generation First generation ethanol, commonly known simply as ‘‘ethanol’’, is a biofuel produced by the fermentation and distillation of sugar- and starch- based raw materials Ethanol from non-edible sources (such as corn stover and sugarcane bagasse) is termed ‘‘second generation ethanol’’, or bioethanol. Large quantities of ethanol is a fermentation inhibitor, therefore molasses have to be diluted

Ethanol feedstocks: Starch Eg. Corn Easy to extract and ferment Food versus Fuel Ubiquitous availability- save transportation costs

Ethanol Feedstocks: Cellulose/Lignocellulose Most common organic compound on earth Found in non-food plant material such as agricultural wastes Considered a “second generation” biofuel, therefore starts comparing to current biofuels Ubiquitous availability- save transportation costs Straw, grasses and wood the issue of transport for cellulosic feedstocks is not as large as it is for corn, due to the fact that cellulosic production in more regions of the country is possible, thus reducing shipment costs. From farm to car, cellulosic ethanol releases less greenhouse gas than gasoline (86 percent less) and corn ethanol (52 percent less than gasoline) Lignocellulosic agricultural residues are an ideal choice since they can be effectively hydrolyzed to fermentable sugars and integrated in the context of a biorefinery without competing with the food supply chain From an environmental point of view, ethanol can reduce sulphur, particulate matter and carbon monoxide emissions, but it may increase atmospheric concentrations of acetaldehyde (CH3CHO), a chemical precursor in the formation of photochemical smog. Additionally, the carbon footprint from ethanol combustion is smaller than that produced by fossil fuels, since plants remove carbon from the environment to produce biomass Compared to corn, cellulosic feedstocks have better energy conversion ratios, cause reduced CO2 emissions, and create less damaging land and water impacts Net positive/negative: Corn- debateable, cellulose: slightly less debateable, biodiesel: positive established (The reason is due mainly to the natural ability of soybeans to fix nitrogen) Costliest input to corn-based ethanol production is nitrogen fertilizer. Soybeans can be grown without, leave the soil nitrogen rich beneficial to follow on crops

Lignocellulose

Plant cell wall components Cellulose Cellulose Lignin Lignin Hemicellulose (need special yeast to convert to ethanol) Extractives Extractives Ash Ash Chapple, 2006; Ladisch, 1979

Lignocellulosic biomass Cellulose Lignin Pretreatment Hemicellulose Amorphous Region Crystalline Region

Ethanol Feedstocks: Marine Algae High growth rates and productivity Low energy demand High carbohydrate content Do not compete with the cultivation of food crops or freshwater supply Nor adversely affect vulnerable ecosystems Able to sustain hostile environments including insufficient nutrients and high salinity.

Comparisons

Barriers to cellulosic ethanol production Refining and production costs Acreage dedicated to growing switchgrass is acreage not dedicated to growing food. Fortunately, enzymes to separate lignin from cellulose This process converts 45% of the biomass energy into ethanol (85% for oil)

Comparison of feedstocks: Potential Yield

Comparison of feedstocks: Ethanol types and gasoline

Bioethanol Properties

Bioethanol versus biodiesel

Current Methodologies

Current Methodologies for bioethanol production Feedstock improvement Pretreatment: Ultrasonication and microwave irradiation Shortening of fermentation time Lowering the enzyme dosages Improving the overall starch hydrolysis Integration of the simultaneous saccharification and fermentation (SSF) process

Different Production Setups

Different Production Setups

Solar-energy driven catalytic reaction Single-step conversion Starch, cellulose, marine algae as feedstock

Solar-energy driven catalytic reaction: Algae

Solar-energy driven catalytic reaction

Solar-energy driven catalytic reaction About 65 day incubation 0.6 g ethanol per day, 8 g ethanol per m2 per day 38 gm of ethanol at the end 85% theoretical yield

Bioethanol: Pros and Cons

Bioethanol: Pros Renewable Complete combustion, cleaner burning Reduction in GHGs Carbon neutral Energy security Better management of spills

Bioethanol: Cons Hygroscopic nature Shipping costs (lack of pipeline system) Corn prices are influenced by the converging demands (food vs fuel) Ethanol more expensive than gasoline on a per gallon basis Lower energy content Can only be used on a specially designed vehicles Lack of availability of E-85 pumping stations. Strain on agricultural production and land use, depletes fresh water supplies and soil resources Distribution hampered by a high level of corrosiveness damaging existing infrastructure May increase atmospheric concentrations of acetaldehyde The production of ethanol places an enormous strain on agricultural production and land use, depletes fresh water supplies and soil resources Distribution of ethanol is hampered by a high level of corrosiveness that damages existing infrastructure Without subsidies, ethanol costs more to produce than gasoline There is a strong body of conflicting data with regard to its net energy output Ethanol’s potential contribution to greenhouse gas impacts are debatable

Questions: Is burning biofuels more environmentally-friendly than burning oil? What are the alternatives for a more sustainable energy system? What are the ways bioethanol production and usage can be improved? What are the incentives for better engine design to incorporate ethanol as fuel? Ways to dry bioethanol to increase purity?

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Questions:

Failures of bioethanol

Failures of bioethanol

Failures of bioethanol

Failures of bioethanol

Different Production Setups

Different Production Setups

Outline What is bioethanol Different sugar sources: Starch, cellulose, lignocellulose, algae General process of bioethanol production: saccharification, fermentation Reactor sketch First/second generation Bioethanol advantages Bioethanol disadvantages Comparison of different kinds of ethanol and gasoline

Cellulosic versus lignocellulosic/hemicellulosic Cellulose is hydrolyzed to glucose, while hemicellulose is decomposed mainly into xylose and other pentoses and hexoses (Figure 2). The hydrolysis of agricultural residues can be achieved by the addition of acid, base or enzymatic catalysts. Need for neutralizing the reaction medium after the process, the high corrosivity and the generation of solid wastes and the generation of degradation products such as acetic acid and furfural