Biofuels are a promising source of renewable energy, but using biomass for energy is nothing new – at the most basic level, humans have been using biomass for energy since prehistoric times. Technically, a ‘biofuel’ is any biomass that has been converted into fuel. This can include bioethanol and algal biodiesel, but it can also include firewood, charcoal, and animal dung.
This blog will look at the evolution of biomass as a fuel source throughout human history.
Historical Use of Biomass
It is unclear when humans began using fire exactly. Early humans most likely saw natural wildfires occur on the African savannah and opportunistically kept them going. The earliest confirmed, controlled fires date back 3-400,000 years, but possible controlled fires have been found from over a million years ago. We do know that by 6-7,000 years ago, humans had widespread knowledge of fire, and used it to modify landscapes for food and energy production.
Past humans used a variety of biomass fuels, the most common being wood and charcoal. Wood was the dominant fuel for heating and cooking from prehistoric times through the 19th century. Charcoal, or wood that has been heated to remove volatile compounds (pyrolyzed), has been found in ancient cave paintings, and the first reference to its use as a fuel is from the 6th century BC. Ancient humans also used vegetable oil to light lamps, especially rapeseed oils.
Biomass Burning Today
Wood and biomass burning continue to be important sources of energy around the world. Today, 6% of the global energy supply comes from wood alone. About 90% of all biomass burning is caused by humans.
However, biomass burning poses serious climate risks. Most obviously, burning vegetation destroys carbon sinks, emits greenhouse gases into the atmosphere, and causes lasting damage to natural landscapes. Burns can also generate brown carbon, a highly variable pollutant that contributes to global warming.
Biofuels as a Replacement for Fossil Fuels
Early Engine Biofuels
While the Industrial Revolution is now associated with fossil fuels, biomass-derived fuels have powered engines and automobiles from the beginning. The first bioethanol-powered engine appeared in 1824, and the first diesel engine, invented in the 1890s, could run on vegetable oil. The first Model T was powered by ethanol as well.
Generally, first-generation biofuels are fuels derived from food crops like corn and sugarcane. These fuels took off throughout the 20th century. During World War II, vegetable oil was used to replace petroleum. Later on, the oil embargo of the 1970s motivated greater investment in biofuels.
Federal and state governments encouraged growth in the industry from the 80s through the early 2000s. In the 80s, subsidies motivated farmers to get into bioethanol production. In 2005, the Energy Policy Act required government fleets to include vehicles that did not use imported gas, which created more room for biofuels on the market; before that, the National Park Service had already adopted biodiesel vehicles. Some US states began requiring regular diesel to include biodiesel additives in the 2000s. Nationally, the Energy Independence Act of 2007, the 2010 National Renewable Fuel Standard, and the Volumetric Ethanol Excise Tax Credit of 2005-2011 created measures to increase biodiesel sales.
One persistent issue with first-gen biofuels is that they compete with food crops for land and resources. As of 2021, 40% of corn went to bioethanol production despite producing only 5% of the nation’s energy needs. In response, researchers have sought alternative biomass sources.
Modern Second-Generation Biofuels
Second-generation biofuels are associated with inedible vegetation, usually cellulosic crops (woody or grass-like plants), or residues from agriculture and forestry. As they don’t use food crops directly, these fuels are supposed to reduce competition between energy and food needs. However, their real impact may be more complex – for example, some second-generation biomass types provide food for livestock, while others require a significant amount of water. Some growing operations may also contribute to land degradation and deforestation. Moreover, processing cellulosic crops into fuel involves more energy, water, and processing.
Modern Third-Generation Biofuels
Third-generation biofuels are associated with algal biomass. Algae are a promising biomass alternative as they multiply rapidly and remove large amounts of CO2 from the atmosphere. While they aren’t very energy-dense, making current algal biofuel processing fairly inefficient, there is ongoing research into engineering new kinds of algae.
Waste-Based Biomass Fuels
Several other processes generate materials that also provide a source of fuel. For example, decomposition in landfills produces methane-rich gases that can be combusted for energy. Similarly, decomposition in wastewater can be used to produce energy, or reactors that decompose organic matter (anaerobic digesters) can be specifically designed for fuel production. Solid waste can also be incinerated in waste-to-energy plants. In a more niche example, paper manufacturing creates a byproduct called ‘black liquor’ from leftover wood mass that can be used as fuel.
Berna, F. and Goldberg, P. 2007. Assessing Paleolithic pyrotechnology and associated hominin behavior in Israel. Isr. J. Earth sci. 56: 107–121.