How Do We Use Biomass?
What is biomass?
Biomass refers to organic matter that comes from plants and animals. It encompasses all biologically-based materials that are available on a renewable basis. Biomass contains stored energy from the sun. Plants absorb sunlight during photosynthesis to produce carbohydrates that form biomass.
Some examples of biomass materials include:
- Wood and wood processing wastes – sawdust, timber slash, wood chips, bark, lumber mill scrap
- Agricultural crops and waste materials – corn, soybeans, sugar cane, switchgrass, wheat, algae
- Food, yard, and wood waste – municipal solid waste, landfill gas, sewage
- Animal manure and human sewage
These biomass feedstocks have traditionally been used for energy production, such as burning wood for heating and cooking. Today, biomass is being used in more advanced ways to produce renewable electricity, transportation fuels, chemicals, and materials.
Traditional uses of biomass
Biomass has been used as an energy source since ancient times when humans first learned how to make fire. The burning of wood and other plant matter provided heat for cooking, warmth, and light. As agriculture developed, vegetative matter such as crops, grasses and trees continued to be the main fuel source for human civilizations until the Industrial Revolution.
In addition to burning biomass directly for heat and energy, traditional agrarian societies made use of organic waste materials. Animal manure has served as an important fertilizer for crops worldwide for thousands of years. Manure helps improve soil fertility and structure, provides nutrients for plant growth, and increases the water holding capacity of soil. The use of manure as fertilizer continues today in organic farming and small-scale agriculture.
Biomass for biofuels
One of the most common uses of biomass today is for the production of transportation biofuels like ethanol and biodiesel. Ethanol is commonly produced from corn, sugar cane, or other starch-based feedstocks through fermentation. The sugars in the biomass are converted by yeast or bacteria into ethanol, which can then be used to power vehicles.
Biodiesel is typically produced from oil crops like soybeans, canola, and palm oil, as well as from waste cooking oils and animal fats. The oils go through a chemical process called transesterification to convert them into biodiesel. Biodiesel can be used on its own or blended with conventional diesel fuel.
Using biomass for biofuels helps reduce dependence on fossil fuels and lowers net carbon emissions because the carbon dioxide released when biofuels are burned is offset by the carbon dioxide absorbed as the biomass feedstocks grow. Ethanol and biodiesel are renewable, domestically produced fuels supporting energy independence and rural economies.
However, large-scale biofuel production has raised some sustainability concerns, such as utilizing arable land that could otherwise be used to grow food crops. Advanced biofuels produced from non-food biomass like grasses, agricultural residues, and algae may provide more scalable and sustainable biofuel production.
Biomass for Heat and Electricity
One of the most common uses of biomass today is burning it to produce heat and electricity. Many power plants have been modified to burn biomass, either on its own or co-fired with coal. When biomass is burned, the chemical energy is released as heat that can be used to boil water. The steam from the boiling water can then spin turbines to generate electricity.
Co-firing coal with biomass is an attractive option for power plants because it does not require extensive infrastructure changes. Coal and biomass can be burned together, reducing the amount of coal needed. Many types of biomass, like wood chips and agricultural residues, can be co-fired at percentages up to 15-20% biomass. Higher percentages of biomass usually require modifications to fuel handling and pulverizing systems.
Dedicated biomass power plants can be built to burn 100% biomass fuels. These plants look similar to coal-fired plants, but require fuel handling systems designed for bulkier biomass material. The boilers, steam turbines and generators are similar. While dedicated plants produce zero net carbon emissions, the upfront capital costs tend to be higher than co-firing.
Overall, burning biomass represents a low-cost and flexible way to produce renewable baseload electricity and take advantage of existing power plant infrastructure. With proper sustainably sourced feedstocks, biomass for heat and power can provide carbon benefits compared to coal alone.
Biomass for bioplastics and chemicals
One exciting use of biomass is to produce plastics, polymers, and solvents that traditionally have relied on fossil fuel feedstocks. Biomass can provide a renewable source for many of the chemicals currently made from petroleum or natural gas.
For example, sugars from corn, sugarcane, and cellulosic biomass can be fermented by microbes to produce lactic acid. This lactic acid can then be polymerized to make polylactic acid or PLA, a bioplastic used in plastic bags, food containers, cups, medical implants, and more.
Plant oils can also be converted into chemical building blocks like ethylene and propylene to manufacture plastics. Soybean and canola oils are common feedstocks, but new research is exploring the use of oils from algae and other biomass sources.
Biomass can also be processed thermochemically to break it down into an intermediate called syngas. Syngas is primarily carbon monoxide and hydrogen, which can then be catalytically converted into many of the basic hydrocarbon chemicals we use today like ethylene, propylene, methanol, ethanol, and more.
Using biomass as a feedstock for bioplastics and green chemicals has the dual benefits of reducing reliance on fossil fuels and also reducing net carbon emissions since the carbon in biomass is part of the natural carbon cycle.
Biomass through waste conversion
One way we can utilize biomass is by converting waste materials into useful energy and products. Specifically, organic waste streams like food waste, agricultural residues, and municipal solid waste contain large amounts of biomass that can be recycled.
Food waste from homes, restaurants, and grocery stores is a major source of biomass that is often sent to landfills. This food waste can be diverted and used for renewable energy instead. Technologies like anaerobic digestion utilize microorganisms to break down food waste and produce biogas, which contains methane that can be used for heating and electricity generation. The remaining digestate material can also be used as a soil amendment.
Agricultural residues like corn stover, sugarcane bagasse, and manure are other forms of organic waste that contain high biomass content. These can be processed using thermal or biological methods to produce various biofuels, bioproducts, and power. For example, stover can be gasified to make syngas, while manure can be converted to biogas in a digester.
Municipal solid waste contains everyday items like paper, cardboard, yard trimmings, wood, and food scraps that are rich in organic matter. This waste can be diverted from landfills and utilized for bioenergy through various processes. Waste-to-energy plants can combust MSW to generate electricity. Anaerobic digestion and other conversion methods can also extract energy and valuable chemicals from these materials.
Converting existing waste streams into bioenergy and bioproducts is a sustainable way to extract value from materials that would otherwise be incinerated or left to decompose in landfills. Waste conversion offers great potential to produce renewable energy while also diverting waste from landfills.
Sourcing biomass sustainably
As demand for biomass increases, it’s crucial that we source it in a sustainable way. Unsustainable harvesting of biomass resources can lead to deforestation, loss of biodiversity, and increased greenhouse gas emissions. There are several key principles for sourcing biomass sustainably:
Sustainable harvesting rates – Only harvest biomass at a pace that allows replenishment of the resource over time. For example, with forests, do not cut down trees faster than the rate of regrowth.
Protect high conservation value areas – Avoid sourcing biomass from forests or other ecosystems with high biodiversity value or that provide important ecosystem services.
Maintain soil health – Use practices like cover crops, crop rotation, and low/no till farming to protect soil quality for future biomass production.
Prioritize waste biomass – Utilize waste residues like forest thinnings, sawmill scrap, or crop residues whenever possible rather than extracting new biomass.
Encourage sustainable practices – Support land managers and farmers to utilize sustainable forest management plans, agricultural practices, and third-party sustainability certifications.
By following these principles, we can scale up biomass usage while protecting our valuable natural resources and ecosystems for the future.
Challenges of using biomass
While biomass offers many benefits as a renewable energy source, expanding its use comes with some challenges. Three major hurdles are the high costs, low energy density, and transportation logistics.
The production, harvest, and processing of biomass feedstocks can be expensive compared to fossil fuels. Facilities require substantial capital investment and advanced technologies to convert biomass efficiently. This makes the energy cost per BTU generally higher than traditional fuels.
Biomass also has a low energy density per volume compared to fossil fuels. This means transporting and storing large amounts of biomass requires more handling and space. Fossil fuels like coal and oil have energy densities up to 10 times higher.
Transporting bulk quantities of biomass sustainably over long distances is difficult logistically. Biomass feedstocks are bulky and can’t be handled like liquid fuels. New infrastructure is needed to move biomass efficiently from suppliers to processing facilities.
Future opportunities
As technology and research continues to advance, there are exciting opportunities to utilize biomass in new and innovative ways in the future. Some of the most promising areas are:
Advanced biofuels
New conversion processes are being developed to produce advanced biofuels from biomass feedstocks that have properties much closer to petroleum-based fuels. These include renewable diesel, biodiesel, ethanol, methanol, butanol and more. Advanced biofuels can serve as direct “drop-in” replacements for existing fuels with no modifications required.
New conversion technologies
Emerging technologies like pyrolysis, hydrothermal liquefaction, and catalytic conversion allow higher efficiency conversion of biomass into fuels and products. These processes are still in development but have significant potential.
Policy incentives
Government policies like renewable fuel standards, carbon pricing, and subsidies for renewable energy sources make biomass more economically viable. Continued policy support can encourage investment and adoption of biomass technologies.
With increased research, supportive policies, and new innovations, biomass is poised to play an even greater role in the future renewable energy landscape.
Conclusion
In summary, biomass provides a versatile renewable resource that can be utilized for a wide range of applications. From traditional uses like home heating and cooking, to modern biofuels, bioplastics and renewable power generation, biomass offers a way to displace fossil resources. Key applications of biomass today include:
- Biofuels like ethanol and biodiesel for transportation
- Renewable heat and electricity
- Bioplastics and chemical feedstocks
- Conversion of organic wastes to energy and fuels
With continued development of efficient technologies and sustainable practices for sourcing biomass, these applications are likely to grow substantially in the future. Using biomass as a renewable alternative to fossil resources will become increasingly important for transitioning to cleaner energy and materials production globally.
Though some challenges remain around land use changes and transportation economics, the outlook for expanding biomass utilization through multiple pathways is promising. With responsible sourcing and conversion, biomass can provide a key pillar in supporting the development of a sustainable bioeconomy.
