Biomass for Power and Heat Generation

There are many potential advantages to using biomass instead of fossil fuels for meeting energy needs. Specific benefits depend upon the intended use and fuel source, but often include: greenhouse gas and other air pollutant reductions, energy cost savings, local economic development, waste reduction, and the security of a domestic fuel supply. In addition, biomass is more flexible (e.g., can generate both power and heat) and reliable (as a non-intermittent resource) as an energy option than many other sources of renewable energy.

Biomass fuels are typically used most efficiently and beneficially when generating both power and heat through CHP (combined heat and power). CHP, also known as cogeneration, is the simultaneous production of electricity and heat from a single fuel source, such as biomass/biogas, natural gas, coal, or oil. CHP provides:

• Distributed generation of electrical and/or mechanical power.
• Waste-heat recovery for heating, cooling, or process applications.
• Seamless system integration for a variety of technologies, thermal applications, and fuel types into existing building infrastructure.

CHP is not a single technology, but an integrated energy system that can be modified depending on the needs of the energy end user. The hallmark of all well-designed CHP systems is an increase in the efficiency of fuel use. By using waste heat recovery technology to capture a significant proportion of heat created as a byproduct in electricity generation, CHP systems typically achieve total system efficiencies of 60 to 80 percent for producing electricity and thermal energy. These efficiency gains improve the economics of using biomass fuels, as well as produce other environmental benefits. More than 60 percent of current biomass-powered electricity generation in the United States is in the form of CHP.

The industrial sector currently produces both steam or hot water and electricity from biomass in CHP facilities in the paper, chemical, wood products, and food-processing industries. These industries are major users of biomass fuels; utilizing the heat and steam in their processes can improve energy efficiency by more than 35 percent. The biggest industrial user of bioenergy is the forest products industry, which consumes 85 percent of all wood waste used for energy in the United States. Manufacturing plants that utilize forest products can typically generate more than half of their own energy from woody waste products and other renewable sources of fuel (e.g., wood chips, black liquor).

Most of the electricity, heat, and steam produced by industrial facilities are consumed on site; however, some manufacturers that produce more electricity than they need on site sell excess power to the grid. Wider use of biomass resources will directly benefit many companies that generate more residues (e.g., wood or processing wastes) than they can use internally. New markets for these excess materials may support business expansion as the residues are purchased for energy generation purposes or new profit centers of renewable energy production may diversify and support the core business of these companies.

Biomass Feedstocks

The success of any biomass-fueled CHP project is heavily dependent on the availability of a suitable biomass feedstock. Biomass feedstocks are widely available in both rural and urban settings and can include:

Rural Resources:

• Forest residues and wood wastes
• Crop residues Energy crops Manure biogas

Urban Resources:

• Urban wood waste
• Wastewater treatment biogas
• Municipal solid waste (MSW) and landfill gas (LFG)
• Food processing residue

Feedstocks vary widely in their sources and fuel characteristics and therefore vary in typical considerations for their utilization. Various biomass resources can require different approaches to collection, storage, and transportation, as well as different considerations regarding the conversion process and power generation technology that they would most effectively fuel.

Process Systems & Design welcomes your inquiries in to biomass processing. With years of engineering experience in this field, PS&D is an outstanding engineering partner for any biomass-to-energy conversion process.

Contact Process Systems & Design by visiting http://www.processsystemsdesign.com or call (410) 861-6437.

From Biomass to Biofuel

Biomass converted to gasoline (image courtesy of epa.gov)

Biomass resources run the gamut from corn kernels to corn stalks, from soybean and canola oils to animal fats, from prairie grasses to hardwoods, and even include algae.

In the long run, we will need diverse technologies to make use of these different energy sources. Some technologies are already developed; others will be. Today, the most common technologies involve biochemical, chemical, and thermochemical conversion processes.




Ethanol, today’s largest volume biofuel, is produced through a biochemical conversion process. In this process, yeasts ferment sugar from starch and sugar crops into ethanol. Most of today’s ethanol is produced from cornstarch or sugarcane. But biochemical conversion techniques can also make use of more abundant “cellulosic” biomass sources such as grasses, trees, and agricultural residues.

Researchers develop processes that use heat, pressure, chemicals, and enzymes to unlock the sugars in cellulosic biomass. The sugars are then fermented to ethanol, typically by using genetically engineered micro- organisms. Cellulosic ethanol is the leading candidate for replacing a large portion of U.S. petroleum use.

A much simpler chemical process is used to produce biodiesel. Today’s biodiesel facilities start with vegetable oils, seed oils, or animal fats and react them with methanol or ethanol in the presence of a catalyst. In addition, genetic engineering work has produced algae with a high lipid content that can be used as another source of biodiesel.

Algae are a form of biomass which could substantially increase our nation’s ability to produce domestic biofuels. Algae and plants can serve as a natural source of oil, which conventional petroleum refineries can convert into jet fuel or diesel fuel—a product known as “green diesel.”

Researchers also explore and develop thermochemical processes for converting biomass to liquid fuels. One such process is pyrolysis, which decomposes biomass by heating it in the absence of air. This produces an oil-like liquid that can be burned like fuel oil or re ned into chemicals and fuels, such as “green gasoline.” Thermochemical processes can also be used to pretreat biomass for conversion to biofuels.

Another thermochemical process is gasification. In this process, heat and a limited amount of oxygen are used to convert biomass into a hot synthesis gas. This “syngas” can be combusted and used to produce electricity in a gas turbine or converted to hydrocarbons, alcohols, ethers, or chemical products. In this process, biomass gasifiers can work side by side with fossil fuel gasifiers for greater flexibility and lower net greenhouse gas emissions.

In the future, biomass-derived components such as carbohydrates, lignins, and triglycerides might also be converted to hydrocarbon fuels. Such fuels can be used in heavy-duty vehicles, jet engines, and other applications that need fuels with higher energy densities than those of ethanol or biodiesel.