What Are Examples Of Advanced Biofuels?

Advanced biofuels are a sustainable fuel option made from renewable biomass like plants and agricultural residues, rather than fossil fuels like oil and coal. They provide a cleaner, greener alternative to conventional gasoline and diesel, and help reduce greenhouse gas emissions that contribute to climate change.

Developing advanced biofuels is important to help meet the world’s energy needs in a more environmentally responsible way. As fossil fuel reserves continue to decline, advanced biofuels can help provide energy security and reduce dependence on petroleum.

There are several different types of advanced biofuels currently in production or development. This article will provide an overview of some of the main options:

Table of Contents

Cellulosic Ethanol

Cellulosic ethanol refers to ethanol that is produced from non-food plant materials such as grasses, woods, and agricultural waste. Some sources include algae in the definition of cellulosic ethanol as well. It is considered a more sustainable biofuel than corn ethanol since it does not divert food crops for fuel production.

Cellulosic ethanol has several advantages over traditional corn ethanol. Since it utilizes waste biomass, crop residues, and non-food plants, it does not compete with food production. This makes it more cost-effective and environmentally sustainable. Cellulosic ethanol also has a better energy balance than corn ethanol, generating more energy than required for its production.

However, there are still challenges to the commercialization of cellulosic ethanol. The complex structure of lignocellulose makes it more difficult to break down and convert to ethanol compared to starches and sugars from corn and sugarcane. Enzymatic and chemical processes are required to separate the sugars prior to fermentation. The technology for cellulosic ethanol production is still developing and costs remain high compared to established first-generation biofuels. But continued research and investment are helping drive down costs and improve efficiencies.

Biodiesel

Biodiesel is one of the most commonly used and readily available advanced biofuels. It is produced from vegetable oils, animal fats, and greases. Soybean oil is the largest source of biodiesel in the United States, but other fats and oils can also be used, such as waste cooking oil and inedible corn oil. Biodiesel can directly replace petroleum-based diesel fuel in vehicles and engines. It is often blended with conventional diesel fuel, with blends ranging from 2% (B2) to 20% (B20) biodiesel. Biodiesel has lower emissions compared to petroleum diesel in carbon monoxide, particulate matter, and hydrocarbons. The use of biodiesel also reduces greenhouse gas emissions, as the carbon in biodiesel came recently from the atmosphere, versus fossil fuels that have been stored underground for millions of years.

Renewable Diesel

Renewable diesel is similar to biodiesel but is made through a different production process. The most common process used is called hydrotreating. This process uses hydrogen to remove oxygen from the vegetable oils and animal fats, resulting in a fuel that is chemically similar to petroleum-based diesel.

The key advantage of renewable diesel over biodiesel is that it is compatible with diesel engines without requiring any engine modifications. Renewable diesel can be blended at much higher levels with petroleum diesel, up to 50% or more. Biodiesel blends are typically no more than 20% due to technical limitations.

Major producers of renewable diesel include Neste, Diamond Green Diesel (a joint venture between Valero Energy and Darling Ingredients), and PREEM. Feedstocks are diverse, including used cooking oil, animal fats, and vegetable oils such as canola, camelina and soybean oil.

The production process of hydrotreated vegetable oils (HVO) results in a cleaner burning fuel that reduces lifecycle greenhouse gas emissions by up to 80% compared to fossil diesel. Renewable diesel is increasingly being used in various transportation applications globally.

Biogas

One type of advanced biofuel is biogas produced from decomposing organic matter such as manure, sewage, food scraps, and plant material. Anaerobic digestion by microorganisms breaks down the organic matter to generate a gas consisting primarily of methane and carbon dioxide. This gas can be collected and used as a renewable fuel source.

Biogas can be produced at facilities such as landfills, wastewater treatment plants, and livestock farms. The methane component can be upgraded into pipeline-quality renewable natural gas, which serves as a direct replacement for fossil natural gas. Biogas can also be refined into biomethane, a nearly pure source of methane.

Biogas offers environmental benefits because its production puts waste materials to productive use. Capturing methane also prevents its release into the atmosphere, where it would contribute to greenhouse gas emissions. The renewable natural gas derived from biogas is considered carbon-neutral when burned because it makes use of existing organic carbon rather than introducing new carbon from fossil sources.

Biojet Fuel

Biojet fuel is an advanced biofuel produced from renewable sources that can be used to replace traditional jet fuel. The main sources used to produce biojet fuel include plant oils, sugars, and alcohols. The advantage of biojet fuel is that it has a smaller carbon footprint compared to regular jet fuel.

Plant oils like camelina, jatropha and algae oil can be refined through a process called hydrotreating to produce a hydrocarbon fuel suitable for use as a drop-in replacement for jet fuel. The hydrotreating process removes oxygen from the oils to create a paraffinic product. Biojet fuels produced from plant oils have very similar properties to conventional jet fuel.

Biojet fuels can also be produced from fermenting plant sugars derived from crops like corn and sugarcane. The sugars are fermented to produce alcohols like ethanol, which can then be chemically converted through additional processes into jet fuel. The conversion processes create hydrocarbon molecules like those found in regular petroleum jet fuel.

The main advantage of biojet fuels is that since they are derived from plants and organic materials, their net carbon emissions are lower than conventional jet fuel over their full life cycle. This makes them more sustainable and environmentally friendly. The production methods for biojet fuels are also continually improving to make them even more efficient and cost effective.

Biobutanol

Biobutanol is an alcohol-based fuel produced from biomass feedstocks like corn, sugar beets, and wheat straw. It has emerged as a promising advanced biofuel due to several advantages over ethanol.

Like ethanol, biobutanol can be produced through fermentation of sugars from starch and cellulose. However, biobutanol has a higher energy content than ethanol, giving it comparable properties to gasoline. Biobutanol contains more carbon and hydrogen atoms per molecule than ethanol.

This allows biobutanol to be blended with gasoline at higher percentages or used as a direct replacement for gasoline in engines. Typical gasoline-biobutanol blends are at 10-20%, compared to 10% for ethanol-gasoline blends.

Biobutanol is also less corrosive than ethanol, making it easier to transport through existing fuel pipelines. Overall, biobutanol provides a more attractive biofuel option as a drop-in gasoline substitute.

Biohydrogen

Biohydrogen is one type of advanced biofuel produced through gasification or fermentation processes. The gasification process involves heating biomass materials like wood or agricultural waste at high temperatures in a low-oxygen environment. This breaks down the biomass into hydrogen and carbon monoxide gases which can then be further processed into biofuels. The fermentation process uses microorganisms like bacteria or algae to convert organic matter into hydrogen gas through anaerobic digestion. Both processes generate hydrogen gas that can be used as a transportation fuel in hydrogen fuel cells.

Compared to other biofuels, biohydrogen offers some advantages. Fuel cells powered by biohydrogen generate only water and heat as byproducts, with no carbon dioxide emissions. Biohydrogen has a high energy density and can provide more power per unit of weight compared to batteries. It can be produced domestically from renewable biomass sources, reducing reliance on imported petroleum. However, there are still technical and economic challenges to overcome before biohydrogen can be widely adopted as a transportation fuel. More research is needed to improve production efficiency and lower costs.

Overall, biohydrogen derived from biomass gasification or fermentation has the potential to provide a clean, renewable fuel for zero-emission vehicles. With further development, it may become a sustainable transportation fuel option that reduces greenhouse gas emissions compared to gasoline and diesel.

Drop-in Fuels

Drop-in fuels are biofuels that are compatible with existing engines and fuel distribution infrastructure. This reduces the need for engine modifications or new delivery systems when switching from conventional to renewable fuels. Drop-in fuels can be blended at high levels with petroleum fuels or potentially replace them entirely.

Some examples of drop-in biofuels include:

Renewable diesel – Produced from fats, oils and greases; chemically similar to petroleum diesel.
Biobutanol – Can directly replace gasoline in high percentage blends.

Fischer-Tropsch fuels – Synthetic diesel and jet fuel derived from biomass.

The key advantage of drop-in biofuels is that they provide an easier transition to renewable energy, without major infrastructure changes. This makes them attractive options for reducing dependence on fossil fuels, especially in the transportation sector. Their compatibility with existing engines also allows for gradual blending, building up renewable content over time.

Conclusion

In summary, there are several types of advanced biofuels that hold promise for the future. Cellulosic ethanol, biodiesel, renewable diesel, biogas, biojet fuel, biobutanol, and biohydrogen are all options that can be produced from non-food crops and agricultural waste products. These advanced biofuels have the potential to provide renewable, low-carbon alternatives to fossil fuels for transportation, aviation, and other sectors.

Looking ahead, research and development will continue to make advanced biofuel production more efficient and cost-effective. With supportive policies and investment, some experts predict advanced biofuels could supply a substantial portion of global transportation fuel demand in the coming decades. However, challenges remain in scaling up production and infrastructure for distribution and use. Overall, advanced biofuels represent an important opportunity to develop sustainable, low-emission energy sources that do not compete with food crops.