Bioenergy technologies

Summary

The introduction of green bioenergy technologies has the promise of reducing pollution and dependence on finite fossil fuels. Bioenergy derived from biomass has the potential to provide renewable and sustained energy on both a local and a global scale. According to the International Energy Agency Bioenergy, the fundamental objective of bioenergy technology is to increase the use and implementation of ecologically sound, economically viable, and sustainable bioenergy that will help meet the world's increasing energy demands.

Definition and Basic Principles

Although they are closely related terms, bioenergy should not be confused with biomass. Fundamentally, bioenergy is energy derived from biomass, that is, energy derived from living, or recently living, biological organisms. Although fossil fuels are naturally occurring substances formed through the decomposition of biological organisms, the creation of these types of fuels takes millions of years. On a human history scale this means they are nonrenewable and unsustainable. The global demand for fossil fuels such as oil continues to increase. Oil has allowed human society to thrive because it has supplied seemingly endless cheap energy, creating diverse industries and employment. Scientific evidence continues to mount, however, in regard to its environmental impact. Oil is also a finite resource, and research has indicated that peak oil has either already occurred or will occur by the mid-twenty-first century. A growing number of environmental and scientific organizations state that once the point of peak oil is reached, demand will far outstrip supply, and therefore, it is imperative that an alternative and sustainable source of fuel is found and implemented.

Background and History

The history of bioenergy is as long as the history of human civilization itself. The most basic form of bioenergy from biomass—the burning of wood for heat and light—has been used for thousands of years. Human society might rely heavily on fossil fuels for its energy needs, but bioenergy has been the world's primary energy source for most of human history and is still in use.

Wood and other combustibles such as corn husks are not the only sources of bioenergy with a long history of human use. One of the most popular biofuels is ethanol. Ethanol was first developed in the early to mid-nineteenth century, before Edwin Drake's 1859 discovery of petroleum. The push for alternative fuels during that time was driven by the need to replace the whale oil used in lamps, as supplies dwindled and prices increased. By the late 1830s, ethanol mixed with naturally derived turpentine was the preferred and cheaper alternative.

In 1826, Samuel Morey invented the internal combustion engine. His engine was powered by a composite fuel of ethanol and turpentine. Although he was unable to find a suitable investor, his engine is considered to be his greatest and most progressive invention. It was not until 1860, however, that the German inventor Nicholas Otto independently invented the internal combustion engine, again fueled by ethanol, and achieved financial backing to develop the engine.

The next considerable leap in interest in bioenergy and in technology development occurred with the invention of the automobile in the early 1900s and Henry Ford's vision of an ethanol-fueled vehicle. As early as 1917, scientists knew that ethanol and other alcohols could be used as fuels. Because ethanol and other alcohols could be derived easily from any vegetable matter that undergoes fermentation, they could be cheaply and easily produced. Despite this, however, ethanol fuels were not widely embraced as the fuel of choice for automobiles. This was particularly true in countries such as the United States where an ethanol tax made the alternative fuel more expensive than petrol. By 1906, when the tax was removed, gasoline fuel had developed an extensive infrastructure, and ethanol could not compete.

Because of rationing and shortages of petrol during World War II, ethanol and other vegetable-based fuels were used extensively. In particular, the use of vegetable-based fuels such as palm oil became common in European colonies in Africa to increase fuel self-sufficiency. During the oil crises of the 1970s, oil prices skyrocketed and oil-dependent countries, such as the United States, became desperate to find a replacement for fossil fuels and to reduce their dependence on oil-producing countries. The 1974 oil embargo was influential in renewing interest in alternative fuels, such as ethanol, particularly in the United States.

Despite the embargo fossil fuels continued to be used in greater quantities than ethanol fuels. Although many automotive fuels are mixed with ethanol, there is still significant room for growth and technological and infrastructure development of bioenergy and biofuels. The potential of biofuels as a sustainable alternative to fossil fuels has once again increased interest in bioenergy. However, there are arguments against the use of bioenergy, particularly the fuel-versus-food debate. Some believe that as long as large numbers of people worldwide do not get enough to eat, using crops for fuel instead of food is misguided and unethical. This controversy will exist until rates of starvation and malnutrition in many developing countries are eradicated.

How It Works

Although scientific debate still surrounds human-influenced climate change and the timing of peak oil, many experts believe that developing sustainable fuels from renewable sources and implementing technology that helps reduce pollution is important and necessary. Bioenergy technologies play an important role in accelerating the adoption of environmentally sound bioenergy at a reasonable cost and in a sustainable manner, thereby helping meet future energy demands.

Bioenergy can be produced from many different biological materials, including wood and various crops, as well as human and animal waste. All these materials can be used to produce electricity and heat. Biomass is the fourth largest energy resource in the world after coal, oil, and natural gas. According to the World Bioenergy Association, in 2022, among renewable energy sources, bioenergy accounted for 70 percent of the world's energy consumption. This percentage differs from country to country and is greater in developing countries, than in developed countries such as the United States. The United States is, however, one of the world's largest biopower generators and possesses much of the world's installed bioenergy capacity. The US Energy Information Administration reports that in 2022, twenty-two percent of electricity produced in the United States came from renewable energy sources, including biomass.

Since the 1990s, bioenergy technologies have experienced continuous development. Generally, these technologies can be divided into two main groups in relation to bioenergy production: energy crops and waste energy. Energy crops, which include trees, sugarcane, and rapeseed, are either combusted or fermented to produce high-energy alcohols such as ethanol and biodiesel that can be used as a replacement for petrol and liquid fuels. Certain waste, including organic waste from agriculture, human and animal effluent, food and plant waste, and industrial residue, can be used to produce methane gas. This methane gas can be combusted to produce steam, which can then be used to turn turbine generators and produce heat and electricity.

Most forms of bioenergy require combustion and thus the release of carbon dioxide into the atmosphere at some stage during their production. This release, however, is offset by the initial absorption of carbon dioxide by the fuel crops during the growing process. According to research, even accounting for all carbon dioxide released as a result of the planting, harvesting, producing, and transporting of bioenergy, net carbon emissions are significantly reduced.

Applications and Products

A number of different types of domestic biomass resources, also referred to as feedstocks, are used to produce bioenergy. These include biomass processing residues such as paper and pulp, agricultural and forestry wastes, urban landfill waste and gas, animal (including human) sewage and manure waste, and land and aquatic crops. There are basically two very important and useful applications of bioenergy: the production of electricity and the replacement of liquid fuels such as petrol.

Electricity Production

Biomass is capable of producing electricity in many different ways. The most commonly used methods include pyrolysis, cofiring, direct-fired/conventional stream method, gasification, anaerobic digestion, and landfill gas collection.

The term “pyrolysis” is derived from the Greek words pyro (meaning fire) and lysys (meaning decomposition). Pyrolysis is a thermochemical conversion technology that involves the combustion of biomass at very high temperatures and its decomposition without oxygen. Although this process is energy consumptive and expensive, it can be used to produce electricity through the creation of pyrolysis oil, biochar, and syngasoil, coke, and gas. These three products can be used for electricity production, as soil fertilizer, and for carbon storage. There are two types of pyrolysis—fast and slow. Fast, or flash, pyrolysis, which uses any organic material as a biomass source, takes place within seconds at temperatures of 300 to 550 degrees Celsius (572 to 932 degrees Fahrenheit) with rapid accumulation of biochar. In slow, or vacuum, pyrolysis, which uses any organic material as a biomass source, the combustion of the biomass occurs within a vacuum to reduce the boiling point and adverse chemical reactions.

Cofiring basically involves the combustion of solid biomass such as wood or agricultural waste with a traditional fossil fuel such as coal to produce energy. Many consider this form of bioenergy to be the most efficient in terms of the existing fossil fuel infrastructure, with its high dependence on coal. In addition, because the combustion of biomass is carbon neutralthe carbon absorbed during growth is equal to the amount released during combustionmixing biomass with coal can assist in reducing net carbon emissions and other pollutants such as sulfur. The production of electricity by this method is considered advantageous because it is inexpensive and makes use of already existing power plants.

The direct-fired/conventional stream method is the most commonly used method of producing bioenergy. This process involves the direct combustion of biomass to produce steam, which then turns turbines that drive generators to produce electricity.

Gasification is another type of thermochemical conversion technology. This is where any organic biomass is converted into its gaseous formknown as syngasand used to produce energy. The process relies on biomass gasifiers that heat solid biomass until it forms a combustible gas. This is often used in power production systems that merge gas and steam turbines to generate electricity. Although this technology is still evolving, it is hoped that gasification of biomass may lead to more efficient bioenergy production. Biomass gasification technologies basically can be categorized as fixed-bed gasification, fluidized-bed gasification, and novel-design gasification.

Anaerobic digestion, a natural biological process, has a long history and involves the decomposition of organic biomass material such as manure and urban solid wastes in an air-deficient environment. Fundamentally, anaerobic digestion involves the production of methane gas through bacteria and archaea activity. This methane gas, also known as a type of biogas, is captured and then used to power turbines and produce electric and heat energy, as well as a soil-enhancement material called digestate. The advantage of this method is that it uses waste, such as wastewater sludge, to produce renewable energy and reduces the amount of greenhouse gas being released into the atmosphere.

The process of landfill gas collection is closely related to anaerobic digestion and involves the capture of gas from the decomposition of landfill urban wastes. Landfill gas, which is about 50 percent methane, 45 percent carbon dioxide, four percent nitrogen, and one percent other gases, is then used to produce energy.

Fuel Production

Liquid biofuels are a significant alternative to petroleum-based vehicle and transportation fuels. Biofuels are attractive because they can be used in already existing vehicles with little modification required and also in the production of electricity. However, the COVID-19 pandemic in 2020 strongly impacted the use of all transportation fuels. While biofuels accounted for about 4.8% of transportation fuels in the world in 2019, this percentage dropped significantly in 2020. However, the International Energy Agency anticipates that by 2025, biofuels will account for 5.4 percent of transportation fuels used throughout the world.

Bioenergy production is generally divided into first-generation and second-generation fuels. The main distinction between these two types of fuels relates to the feedstock used. First-generation fuels are already in commercial production in many countries and are primarily made from edible grains, sugars, or seeds. The two most common biofuels are ethanol and biodiesel, both of which are already used in large quantities in many countries. Second-generation fuels are considered superior to first-generation fuels because they are primarily made from nonedible whole plants or waste from food crops such as husks and stalks.

Ethanol, also known as ethyl alcohol, is an alcohol that can be used as a vehicle or transportation fuel. It is a renewable energy produced from sustainable agricultural feedstocks, particularly sugar and starch crops such as sugarcane, potatoes, and maize. Although it can be used as a direct replacement fuel, it is more commonly used as a fuel additive. Many vehicles use ethanol-petrol blends of 10 percent ethanol, which improve octane and decrease emissions. Ethanol is particularly popular in Brazil and the United States, which together produce most of the world's ethanol. Brazil has been at the forefront of ethanol use and as early as 1976 mandated the use of ethanol with fuels, eventually requiring a blend containing 25 percent ethanolthe most of any country. Although using arable land to grow crops to produce ethanol is somewhat controversial, the development of ethanol from cellulosic biomassobtained from the cellulose of trees and grassesis considered promising and may play a large role in the future of ethanol as a biofuel.

Biodiesel is a renewable energy produced from sustainable animal fat and vegetable oil feedstocks, such as soy, rapeseed, sunflowers, palm oil, hemp, and algae, and can be used as a vehicle or transportation fuel. As with ethanol, however, biodiesel is more often used as a diesel additive to reduce the levels of pollution emitted by traditional diesel engines. It is primarily produced through a process known as transesterification, which is the exchange or conversion of an organic acid ester into another ester.

Biobutanol can be used as fuel in internal combustion engines. It is usually produced from the fermentation of biomass, and because of its chemical properties, it is actually more similar to petrol than ethanol is. It can be produced from the same feedstocks used for ethanol production, such as corn, sugarcane, potatoes, and wheat. Despite its possible applications, however, the US Department of Energy reported in April 2020, regulatory hurdles made it difficult to sell biobutanol as a transportation fuel in the United States. However, in 2018, the Environmental Protection Agency (EPA) approved blends containing sixteen percent biobutanol, with the remaining 84 percent being gasoline.

Careers and Course Work

Undergraduate and graduate courses in bioenergy technology are offered at many universities. Most students who follow this path have a strong background in science, agriculture, and fuel production technology. Following graduation, students studying bioenergy technology will understand methods for improving the efficiency of new energy technologies and have a solid understanding of environmentally friendly bioenergy concepts, theories, processes, and practices. These include biology and plant production, bioenergy electricity and fuel production from crops and waste, combustion science, sustainability in energy production, agricultural engineering, power-engine design, and emission-reduction techniques. They will also know how to integrate environmental issues and global economics into decision making. The primary purpose in bioenergy course work and research is to provide students with an understanding of energy as it relates to both economics and the environment. In addition, as with many modern sciences, students of bioenergy technology will require an understanding of computer modeling.

Bioenergy technology responds to the ever-changing needs of human society in relation to renewable and sustainable energy requirements, while focusing on environmental engineering in an internationally, socially, and ecologically responsible way. Students involved in bioenergy technology research and application can pursue various careers in environmental auditing and consulting, bioenergy education, agricultural and combustion engineering, sustainable agriculture, farm energy specializations, power plant and steam boiler engineering, pollution prevention and emissions reduction, waste treatment, renewable energy program management, and project and resource management. These careers span a wide range of industries and sectors, including, most prominently, the energy industry, private sector, nongovernmental organizations, specialized government organizations and agencies, and universities and institutions undertaking teaching and research.

Social Context and Future Prospects

The concept of bioenergy relies on the fact that such energy is sustainable. Although many believe bioenergy is synonymous with green energy, this is not always the case. Individual types of bioenergy produced in different ways and from various biomasses can have very diverse environmental impacts. Although the goal of bioenergy is to reduce the world's dependence on nonrenewable (to all intents and purposes) fossil fuels and thereby reduce greenhouse gas emissions and pollution, some forms of bioenergy can be equally harmful in terms of pollution or the energy expended to produce the bioenergy. As such, there have been significant movements since the 1980s to develop cleaner, greener, and move advanced biofuels and technologies. Many countries are investigating the potential of bioenergy, and many researchers believe that bioenergy will become a key contributor to sustainable global energy use.

Biofuels are, however, controversial, and some are calling for a moratorium on their use and advancement because of environmental and social concerns. A concern often cited is the loss of biodiversity and habitat destruction and the use of crops for fuel rather than food. First-generation fuels, already in commercial production in many countries, have been criticized because they are obtained from edible seeds and plants. However, because of the increasing problems of fossil fuel dependence, many of the world's governments and international organizations are stepping up research into bioenergy as a viable and sustainable alternative fuel. Many researchers believe that investigation and implementation of second-generation fuels, which are made from nonedible whole plants or waste from food crops, is the way of the future in terms of both efficiency and social responsibility. Biomass does offer many countries the opportunity to use fuels that are both sustainable and domestically sourced.

According to the EIA, biofuel demand will expand by ten million gallons in the five-year period from 2023-2028. In 2028, expected biofuel demand will be at 52 million gallons. Renewable diesel and ethanol will account for almost 70% of this increase.

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