As countries worldwide move away from fossil fuels to lower their carbon footprints, they turn to renewable energy sources. Just like coal, oil, gas, or other non-renewable energy sources, biomass releases carbon dioxide when burned. However, in contrast, it can actually be a carbon-neutral energy source. When organic materials used to make biomass are replaced in the environment, whether through replanting or farming, it provides a sustainable energy solution.
The versatility of biomass energy is a big part of what makes it so useful, as it can be used to generate heat directly or indirectly, to produce electricity, or in combination to supply both electricity and heat. Also, biomass can be turned into liquid fuel for vehicles or power generators. Done correctly, biomass energy production can prevent many of the negative impacts of refining fossil fuels, including preventing damage to fragile ecosystems.
How Biomass Energy Works
So, what is biomass energy? Essentially, biomass is just chemical energy stored in plants (and animals) that initially emanates from the sun. Photosynthesis generates plant biomass, whereas animal waste converted into biomass also comes from plants and animals that are eaten and discarded as waste through an animal’s feces or via death. Much of this biomass can be burned directly to create heat, but it can also be converted to renewable fuels via various processes.
Sources of biomass energy include:
- Dedicated energy crops and agricultural waste from plants such as algae, corn, soybeans, switchgrass, and woody plants are used mainly for biofuel production.
- Human sewage and animal manure are used for methane and biogas production.
- Solid waste from municipalities like cotton clothing, discarded food, paper, tree branches, and other organic yard waste, wool, and other biogenic materials.
- Wood and waste from wood processing, including sawdust, wood chips, wood pellets, and paper and pulp milling.
In many respects, energy from biomass is produced in the same way as that of fossil fuels, which are made up of long-dead plants and animals. The main difference between the two is that fossil fuels take millions of years to form and release carbon into the atmosphere when burned, whereas biomass relies on processes that are sustainable and remove carbon from the atmosphere. This is especially true when it comes to crops or other plants raised for energy production, which when replanted can make the process carbon neutral.
Processes for Converting Biomass Into Energy
There are four main processes by which biomass is converted into energy. With direct combustion, burning of organic matter directly produces heat energy. Thermochemical conversion uses biomass to produce gaseous, liquid and solid fuels. Liquid fuels can also be made from biomass through a chemical conversion. Additionally, gaseous and liquid fuels can be made from biomass via biological conversion.
The most common means for generating energy from biomass is direct combustion. Biomass can be used to create heat for buildings or industrial processes via burning it directly. Steam turbines can also use biomass to generate electricity via direct combustion.
The two main methods for converting biomass into energy thermochemically are gasification and pyrolysis, which use thermal decomposition to produce energy from biomass feedstock. This involves heating the feedstock material within gasifiers at high temperatures and pressures. The two processes differ in the amount of oxygen present and processing temperatures used.
Pyrolysis uses a nearly oxygen-free environment to heat biomass to 800–900°F (427–482°C), producing fuels like biodiesel, bio-oil, charcoal, methane, and hydrogen. In bio-oil production, the process uses hydrotreatments via a quick pyrolysis that elevates temperatures and pressures. Hydrotreating biomass can produce renewable jet fuels, gasoline, and diesel using a catalyst.
With gasification, biomass is exposed to temperatures between 1,400–1700°F (760–927°C). The process also involves injecting precisely measured amounts of free oxygen, steam, or both to produce both carbon monoxide and syngas, a hydrogen-rich gas. Diesel engines and gas turbines used for electricity production can run on syngas and be utilized directly for heating. Also, hydrogen can be separated from this gas for fuel cells, which can also produce liquid fuels.
The conversion process for transforming biomass chemically is called transesterification. This process converts animal fats, grease, and vegetable oils, along with other fats and oils, into what’s known as fatty acid methyl esters (FAME). Used to produce biodiesel, FAME consists primarily of triglycerides. These are three long chains of molecules containing straight fatty acid connected to a glycerol molecule. This connection involves deactivating oxygen atoms to enable the building of new chemical bonds.
Initially, FAME involves pretreating feedstock similarly to how edible vegetable oils are refined. The primary step for converting biomass through this method involves removing contaminants and waste, particularly solids and unsaponifiable substances, which are insoluble in water but dissolve in organic solvents. This process can also use waste-based feedstocks to produce biodiesel, which involves converting free fatty acids (FFA) into FAME. Different acids can be used for this conversion, both with or without catalysts, which involves high temperatures and pressures and alcohol in certain cases.
Renewable natural gas and ethanol are made via biological processes involving fermentation. Known as biomethane or biogas, sustainable natural gas can be made using anaerobic digesters that break down microorganisms in biological material within oxygen-free environments. As a sequence of processes, anaerobic digestion is used to produce fuel in sewage treatment plants and various livestock operations in much the same way as fermentation is utilized in food and drink production. Biological processes that produce biomethane also occur naturally in landfills for solid waste, which can be captured and used like natural gas sourced for underground gas fields.
Ethanol can be used as an additive to fuels for gasoline-powered vehicles or certain internal combustion engines that can run off 100 percent ethanol. Most fuel ethanol is made from fermented sugars found in grain starch – commonly from barley, corn, and sorghum – as well as from sugar from sugarcane and sugar beets. Fuel-based ethanol additionally contains denaturants that make it undrinkable.
Heyl Patterson: Thermal Processing Equipment for Biomass Energy Conversion
For calcining and drying as well as cooling biomass, Heyl Patterson Thermal Processing provides energy-efficient, innovative, and reliable solutions. Our team of engineers and other professionals have plenty of experience in custom-engineering thermal processing machinery like rotary calciners, fluid bed dryers, and rotary dryers that can handle biomass material for sustainable energy production.
Rotary calciners made by Heyl Patterson can be used for biomass processes that deal with combustible, oxidation-sensitive, and heat-sensitive material. With capabilities that segregate the heat source from the material, our rotary calciners work well for carbonizing biomass into charcoal or the thermal pretreatment process of torrefaction to convert biogas into a coal substitute.
Specifications for our rotary calciners include:
- Can be specially constructed from materials to withstand high temperatures, corrosion, or both
- Gas flow designs that allow airflow in the same or opposite direction of material
- Handles operating temperatures up to 2200°F (1204°C)
- Sizing to over 100 feet (30.48 meters) in length and up to 12 feet (3.6576 meters) diameter
- Various configurations available for heating zone
- Works in dehumidified, inert, oxidizing, or reducing process atmospheres
Fluid Bed Dryers
Heyl Patterson’s fluid bed dryers can handle free-flowing biomass materials, including those derived from grains, waste materials, and wood. Our fluid bed dryers utilize a fluidizing method that’s both energy-efficient and allows a high heat transfer rate. Offering three types of fluid bed, dryers come with either a circular type, trough-type, or vibrating fluid bed.
Specifications for our fluid bed dryers include:
- Allows use of various types of control systems
- Cylindrical design option that back-mixes via both continuous or batch flow, resulting in non-uniform moisture content
- Design option for fluidized media that can process lumpy, sticky, and other difficult-to-handle materials
- Features bedplate made from stainless steel or high-temperature alloy, or else a refractory brick dome design
- Handles operating temperatures for inlet gas up to 2200°F (1204°C)
- Rectangular, plug-flow design option for continuous flow, allowing different gas inlets and resulting in uniform moisture content
- Sizing to diameters up to 18 feet (5.4864 meters), or equivalent diagonal for rectangular design
As one of the most versatile rotary dryers on the market, Heyl Patterson’s rotary dryers are capable of working with an array of biomass bulk solids. Our rotary dryers allow manufacturers to specify moisture content from both starting and finishing stages, biomass temperature, air temperature, air velocity, and how long the material will be retained. Designs for our rotary dryers include external or internal water cooled, counter-current air swept, or combined cooling via both air and water.
Specifications for our rotary dryers include:
- Airflow systems that are forced-draft, induced-draft or a combination of both
- Enables use of various types of control systems
- Features lifting flight design that uses material testing to establish better efficiency in conveying and drying
- Gas flow designs that allow airflow in the same or opposite direction of material
- Handles inlet gas operating temperatures up to 2200°F (1204°C)
- Sizing to over 100 feet (30.48 meters) long and up to 16 feet (4.8768 meters) diameter
Heyl Patterson makes a variety of other thermal processing equipment, including industrial dryers and flash dryers. To learn more about our products and services, contact our team today.