Biofuels Lecture – Key Concepts
Energy and Biotechnology
Energy might not be the first topic associated with biotechnology, but the search for alternative fuels (biofuels) is driven by the desire to:
Lower carbon footprints by reducing reliance on fossil fuels and decreasing greenhouse gas emissions.
Maintain lifestyles by ensuring energy availability for:
Transportation.
Heating.
Electrical power.
Biofuels Overview
Focus: Ethanol, contrasting first and second-generation ethanol, including production methods and environmental impacts.
Other Topics:
Biodiesel: Production processes, feedstocks, and performance characteristics.
Alternatives like green bio-hydrogen and other biofuels: Advanced biofuels and their potential.
Energy Consumption
Energy is vital for:
Transportation (moving people and goods): Affecting supply chains and personal mobility.
Industry (manufacturing): Powering machinery and industrial processes.
Domestic heating (in some countries): Essential for comfort and safety.
Energy Sources
Fossil Fuels: Coal, oil, and gas: Dominant sources with high carbon emissions.
Renewables: Wind, solar, hydroelectric: Cleaner alternatives but with intermittency challenges.
Biofuels & Emerging Technologies: Including hydrogen: Promising options with ongoing research and development.
Motivation for Alternative Fuels
The primary motivation is to reduce carbon emissions per KJ or kilowatt produced: Mitigating climate change.
Industrialization has led to a net release of carbon into the atmosphere: Causing global warming and related issues.
Sudden Rate of Increase in CO_2:
Pre-industrial levels: around 280 parts per million (ppm).
Current levels: exceeding 420 ppm.
Most of the rise occurred in the last 100 years.
Attributed to the combustion of fossil fuels.
Population Growth: Global population since 1750 has increased tenfold: Increasing energy demand.
Increased per capita energy consumption: Further exacerbating energy-related emissions.
BP Energy Reports
British Petroleum (BP) produces energy reports: Providing insights into energy trends and future scenarios.
BP reports describe three scenarios for minimizing carbon emissions in 2023:
Net Zero: Most aggressive approach (blue line): Achieving carbon neutrality.
Accelerated Approach: Rapid transition to renewables and electrification.
New Momentum: Minimal approach: Gradual changes with limited impact.
Goal: Lower net emissions, with net-zero being the most aggressive target: Aiming for significant reductions to combat climate change.
Sources of Carbon Emissions
Industry: Manufacturing processes and heavy industries.
Transportation: Vehicles, aviation, and shipping.
Flaring of natural gas at oil refineries: Wasting valuable energy and emitting greenhouse gases.
Methane emissions from energy production: A potent greenhouse gas with a short lifespan.
Strategies to Lower Climate Impact
Reducing the use of fossil fuels: Transitioning to cleaner energy sources.
Increasing the use of renewables:
Wind: Harnessing wind energy through turbines.
Solar: Capturing solar energy with photovoltaic panels.
Biofuels: Using biomass-derived fuels.
Green hydrogen: Producing hydrogen from renewable sources.
Potential Contribution of Various Strategies
Lowering fossil fuel use: Reducing reliance on carbon-intensive sources.
Increasing renewables use: Expanding the deployment of clean energy technologies.
Introducing hydrogen into the energy market at scale: Utilizing hydrogen as a versatile energy carrier.
Increased electrification of domestic and industrial energy use: Shifting towards electricity-powered systems.
Bioenergy Demand
Predicted increase in demand for bioenergy:
Solid fuels: Timber, wood, wood pellets: For heating and power generation.
Liquid biofuels: For transportation and industrial uses.
Solid biofuels may need to be co-fired with coal and gas for heating and electricity: Improving efficiency and reducing emissions.
Liquid biofuels are mainly for transportation (terrestrial and marine): Reducing reliance on petroleum-based fuels.
Liquid Biofuels Focus
Biotechnology innovations can improve the economics and technologies around liquid biofuels: Enhancing production efficiency and sustainability.
Biomass to energy conversion:
Biomass includes crops, grasses, and forestry waste: Utilizing organic matter for energy production.
Process:
Harvesting, collection, and transportation to a site: Gathering biomass for processing.
Conversion through heating, biochemical processes, or both: Transforming biomass into usable energy forms.
Combustion in engines or heaters to generate heat, electricity, or motive power: Utilizing biofuels for energy generation.
Liquid Biofuels Usage
Liquid biofuels represent about 5-10% of global liquid fuel use: A growing share of the transportation fuel market.
The US has incentives to develop bio-ethanol and biodiesel transportation fuels: Promoting domestic biofuel production.
Existing infrastructure to distribute liquid biofuels (petroleum and diesel): Facilitating integration into the energy system.
Used for various types of transport, with some displacement by electric engines: Reducing greenhouse gas emissions from transportation.
Net lower emissions compared to straight petroleum fuels, even with blended fuels: Offering environmental benefits over conventional fuels.
Sovereign Risk in Australia
Australia produces and refines less than 10% of its liquid fuels: High dependence on imports.
Heavy reliance on transportation liquid fuels from Singapore: Vulnerability to supply disruptions.
Interruption of shipping lines poses a serious sovereign risk: Emphasizing the need for energy security.
Advantages of Liquid Fuels
Relatively high energy density (kilojoules per unit volume or mass): Allowing for efficient storage and transport.
Easy to refuel: Similar to conventional fuels, providing convenience for users.
Existing infrastructure: Compatible with current distribution networks.
Reasonably easy to handle and transport: Enhancing practicality and usability.
Historical Disadvantages of Oil
Diminishing availability of cheap and accessible oil fields: Increasing costs and geopolitical tensions.
Subject to geopolitics due to concentrated fuel sources: Creating supply vulnerabilities.
Strategies to Limit Carbon Emissions in Transport
Greater efficiency in engines: Improving fuel economy.
Use of hybrid and electric engines: Reducing reliance on fossil fuels.
Electric vehicles powered by wind and solar sources: Maximizing environmental benefits.
Emergence of hydrogen-powered vehicles: Exploring alternative fuel options.
MIT Carbon Counter App
Massachusetts Institute of Technology (MIT) Carbon Counter app compares cars and their greenhouse gas emissions: Providing data-driven insights.
Compares cost (vehicle and running costs) versus life cycle emissions: Helping consumers make informed decisions.
Battery electric vehicles have the lowest life cycle emissions: Offering the most sustainable transportation option.
Petroleum cars have the highest life cycle emissions: Contributing significantly to climate change.
Examples of Biofuels
Ethanol and biodiesel are main examples: Widely used and researched biofuels.
Definition: Biofuel carbon source directly derived from biomass (plants): Emphasizing renewable origin.
Involves chemical or biochemical conversion to make a tractable fuel: Processing biomass into usable fuel forms.
Carbon released upon combustion is recently captured through photosynthesis: Contributing to a closed carbon cycle.
Ethanol Sources
Sugar and molasses (from tropical regions): Readily fermentable sources.
Hydrolyzed starches (enzyme conversion to fermentable glucose): Utilizing enzymatic processes.
Second-generation: conversion of lignocellulose into fermentable substrates: Exploring non-food feedstocks.
Biodiesel Sources
Plant oils (e.g., canola oil) or waste oils from food outlets: Diverse sources for biodiesel production.
Esterification to make an ester-based fuel: Converting oils into biodiesel.
Other Biofuels
Solid biofuels for heating and electricity: Using biomass for power generation.
Methane and green hydrogen for energy generation (electricity and heating): Exploring alternative energy carriers.
Volumetric Energy Density of Fuels
Diesel has the highest energy density per unit volume: Providing efficient energy storage.
Biodiesel has 5-10% less energy density than conventional diesel: Slightly reducing fuel economy.
Gasoline (petrol) has a significantly higher energy density than ethanol: Affecting fuel consumption.
A 10% ethanol blend results in a marginal decrease in fuel energy density (3-4% difference compared to conventional gasoline): Minimal impact on performance.
Biobutanol is another alcohol-based fuel produced by fermentation: Offering a potential alternative to ethanol.
Ethanol Production
Primarily produced by yeast-based fermentation: Utilizing microbial processes.
Used for: combustible ethanol for drinking, industrial solvent, liquid fuel: Versatile applications.
High octane efficiency (greater than 100): Improving engine performance.
Ethanol Blends
Mostly blended with petroleum rather than used in high concentrations (80% or above), except in countries like Brazil: Balancing performance and emissions.
Benefits of Ethanol
Lower carbon monoxide (CO) emissions: Reducing air pollution.
Reduced NOx emissions: Decreasing smog formation.
Disadvantages of Ethanol
Low energy density: Requiring more fuel for the same energy output.
Increased emissions of potential toxic chemicals like formaldehyde: Raising health concerns.
Energy Returned on Energy Invested (ERoEI)
Complex calculation to determine the ratio of energy received when combusted compared to the energy invested to make the fuel: Assessing sustainability.
Considers agricultural process, harvesting, transformation to fermentable substrate, distillation, molecular sieving, and distribution: Evaluating the entire lifecycle.
Ethanol as a Blended Fuel in Australia
E5 to E10 is most common; most engines can accommodate this with no real effect: Ensuring compatibility with existing vehicles.
Ethanol Production Process
Primary distillation or continuous distillation to separate ethanol and water up to 96% ethanol: Separating ethanol from the fermentation mixture.
Azeotrope: When relative volatility of ethanol and water are the same, preventing further separation by distillation: Requiring special techniques.
Molecular sieving: Used to get anhydrous ethanol for mixing with gasoline: Ensuring fuel quality.
Biodiesel (Fatty Acid Methyl Ester - FAME)
Formed by a transesterification reaction where plant oil is mixed with methanol and a catalyst (usually methanol and sodium hydroxide): Converting oils into biodiesel.
Can also be achieved using industrial lipases: Exploring enzymatic processes.
Diesel Engines and Biodiesel
Diesel engines are more forgiving in terms of blending: Allowing for higher biodiesel concentrations.
B10 or B20 is commonly used: Balancing performance and emissions.
Generators can often be adapted to run on 100% biodiesel: Promoting wider adoption.
Some farms use 100% biodiesel in tractors and energy generators: Demonstrating practical applications.
Benefits of Biodiesel
Lower carbon oxide emissions due to oxygen content: Reducing greenhouse gas emissions.
Lower emission of particulates compared to 100% conventional diesel: Improving air quality.
First, Second, and Third Generation Fuels
First Generation Fuels:
Carbon source is a food crop, leading to food vs. fuel debate: Raising ethical concerns.
Examples: Ethanol from corn starch, biodiesel from soybean oil.
Second Generation Fuels:
Carbon source is not primarily used as food; byproduct or waste product of some primary activity: Mitigating food security issues.
Examples: Timber waste, lignocellulosic material, sugar cane bagasse.
Lower costs due to no other market for the material: Improving economic viability.
Higher input costs to convert lignocellulose into fermentable material: Requiring advanced technologies.
Examples: Waste vegetable oil biodiesel, cellulosic ethanol.
Third Generation Fuels:
Not using a food resource and not competing for food or arable land: Maximizing sustainability.
Example: Oils extracted from microalgae grown in hyper-saline ponds.
Ethanol Production Reaction
Yeast (like Saccharomyces) converts glucose to ethanol and carbon dioxide in the reaction:
C6H{12}O6 \rightarrow 2 C2H5OH + 2 CO2
The yeast fermentation is not carbon neutral, as it liberates CO_2.
Yeast runs the reaction to generate energy (ATP) for cellular biosynthesis; ethanol is a waste product.
In glycolysis, glucose becomes pyruvate, and NADH is oxidized to keep the cycle running, converting pyruvate to ethanol.
Starches and Ethanol Production
Yeast cannot directly access starches (polymers of glucose):
Starch needs to be broken down into glucose by enzymes in a pretreatment step called hydrolysis:
Industrial production of amylases largely goes into starch conversion:
Starch Composition
Storage polymer in plants consisting of amylose and amylopectin:
Glucose monomers are linked by A1-4 and A1-6 ether linkages:
Enzymes like Termamyl and AMG (commercial enzymes from Novozymes) hydrolyze these linkages, liberating sugar molecules for fermentation:
Closed Carbon Cycle Concept
Photosynthetic process captures CO_2 in the presence of light to create sugars:
Sugars are converted into polymers, creating plant structure and liberating oxygen:
Crops are harvested, sugars are extracted, and fermentation by yeast generates ethanol and carbon dioxide:
Ethanol is purified, dried, and combusted, liberating CO_2 again:
Overall, it's a conversion of light into heat, which can be converted into motive force:
Net reaction: light \rightarrow heat
Ethanol Production Process
First Generation Processes:
Sugars from sugar syrups or molasses can be directly fermented:
Starch from corn or wheat is milled, followed by hydrolysis using amylase enzymes:
Resulting porridge or mash goes into fermenters with yeast and nutrients:
Fermentation proceeds, followed by distillation and molecular sieving to make anhydrous ethanol:
Byproducts can be sold into the agricultural feed industry:
History of Ethanol Production
This process has been known for thousands of years; alcohol production dates back to at least 6000 BC in Samaria:
As a fuel, it has increased in usage over the last 20-30 years, particularly in Brazil and the US:
Ethanol Potential per Crop
Sugarcane yields the highest potential amount of ethanol per hectare per year due to intensive cultivation:
Energy Returned On Energy Invested (ERoEI) in Biofuels
Calculation to determine the ratio of energy in the fuel produced to the energy expended in production:
Bioethanol Plants in Australia
Three bioethanol plants:
Mildura Ethanol: Largest; processes wheat starch near Nowra, NSW (>300 million liters/year):
Sorghum-based refinery northwest of Brisbane:
Serena Distillery: Uses sugarcane molasses south of Mackay, QLD:
Cellulosic Ethanol
Requires conversion of other parts of the plant (e.g., cilose) into fermentable forms:
Energy Distribution in Sugarcane
Sucrose (sugar): One-third of the energy:
Tops and leaves: Another third:
Bagasse (leftover plant material): The remaining third:
Goal of second-generation fuels is to capture energy in these other components by converting cellulose and hemicellulose:
Second Generation Fuels Pretreatment
Requires pressure, heat, and separation of inhibitory products (e.g., perforal from lignin breakdown):
Mechanical and heat processes break plant fibers and make cellulose accessible:
Second Generation Fuels Process
Hydrolysis using a complex mixture of enzymes to convert cellulose into sugars and hemicellulose into pentose sugars:
Engineered yeast or bacteria for fermentation:
Downstream processing is the same as for first-generation ethanol:
Advantages of Ligno-Cellulosic Ethanol
Greater energy extraction from the crop:
Resource does not compete with food markets:
Greater greenhouse gas reduction potential:
Disadvantages of Ligno-Cellulosic Ethanol
Technology has been difficult to implement:
Intractable resource compared to starch:
Lignin fraction has to be utilized differently:
Few successful second-generation ethanol plants despite investment:
Comparison of First and Second Generation Processes
Sugar: Limited pretreatment, straight to fermentation, recovery through distillation:
Starches: Enzymatic hydrolysis step, fermentation, recovery:
Felligno cellulose: Pretreatment, fractionation, enzymatic controls, is again is fermentation and recovery:
Cheaper resources in the second generation, but more intensive and costly processing:
Biodiesel Plants
Widely found in Europe and the US:
Used as a replacement for conventional diesel:
Conversion of plant oil (vegetable oil) in a transesterification reaction to yield the fuel:
Biodiesel Feedstocks
Food oils:
Waste vegetable oils:
Fats from animal processing:
Jatropha (grows in marginal lands, not a combustible oil):
Straight Vegetable Oil vs. Biodiesel
Straight vegetable oil can be burned in some engines but creates viscosity and gelling problems, especially in cold climates:
Biodiesel is a preferred route to create a fuel without these problems; it's essentially an upgrading of raw vegetable oils in a transesterification reaction:
Bio Diesels Reaction
Oils are mixtures of monoglycerides, diglycerides, and triglycerides. Oils are considered triglycerides comprising of Glycerol backbone and fatty acids from the oils linked here.
Methanol with some Catalysis, liberates the glycerol backbone.
Triglyceride + Methanol \xrightarrow{catalysis} Glycerol + Fatty \, Acid \, Methyl\, Ester