Energy: Past, Present, and Future

Farming Alternative Energy - focus on BIOFUEL

Despite federal and state programs to convert corn into ethanol and soybeans into biodiesel to fuel cars and trucks, the United States had never regarded farming as a primary energy producer.  That changed when Congress in August passed the climate provisions of the Inflation Reduction Act, which provides $140 billion in tax incentives, loans and grants to replace fossil fuels with cleaner renewable energy that lowers emissions of carbon dioxide.¹⁵

There are a range of existing, and yet to be fully operationalized, energy sources which are categorized as alternative/renewable energy which students should be familiar with.  As part of their learning students will investigate solar, wind power, hydrogen fuel cell, and hydropower.  Students will also spend some time investigating how our school gets/uses energy.  This overview of energy technologies will be a jumping off point for digging in deeper on the focus of our exploration.  Many – if not all – of these alternatives to fossil fuels have some role to play in cleaning and greening the agriculture, food and natural resources sector’s carbon footprint.  Here I am focusing solely on fuels that are made directly from biomass, and specifically those that can utilize agricultural and food waste in their production.  We will be making and analyzing three biofuels in our classroom, and urban ag lab (outdoors); bioethanol, biogas and biodiesel.  We will, of course also be growing energy, in the form of food, and composting food and garden waste.  Each of these biofuels offers different opportunities for production and use, as described below.

Bio-digestion: what? how? pros/cons

Bio-digestion is a process that mimics the process that occurs when a cow eats grass, and liberates the energy from cellulosic plant material such as hay and grass in their rumen.  The bio-digestion process utilizes the same bacteria as cows in an anaerobic (oxygen free) environment to metabolize/digest a range of organic waste and to generate burnable bio-methane gas also called renewable natural gas. This gas can be used for cooking, heating, or energy generation. This can be done on a home, farm or industrial scale.

Bio-digestion be used to divert and productively utilize a significant amount of organic waste, from municipal waste streams and sewage treatment plants. We waste a lot of food. “…60 million metric tons of food waste is generated just in the US each year, amounting to about 30% of the total food supply,” according to the US Department of Agriculture.¹⁶ 

Digesters have been used most widely on dairy farms, to convert manure to fuel, but also to measurably reduce the manure odor, GHG emissions, and to protect waterways.  I have met several farmers who power their farms and surrounding communities with energy generated from the manure from their dairy herds.  Their neighbors are happy about the low-cost energy, but thrilled that the air outside and inside their homes no longer smells like, well, manure. The American Biogas Council estimates a large increase in demand for bio digestion.  They “count more than 15,000 new sites ripe for development today: 8,600 dairy, poultry, and swine farms; 4,000 water resource recovery facilities, 2,000 food scrap-only systems, and utilizing the gas at 470 landfills who are flaring their gas.”¹⁷

We have invested in a home-scale biodigester, which once set up and running, should provide several hours of cooking gas each week.  Students will learn how to set up and tend this biodigester, and track food and garden waste that is diverted from the waste stream and cook meals with vegetables and herbs grown in our garden, on gas produced with garden and food waste, and use the byproducts of the process to fertilize the garden again.  These digesters require tending, and work most effectively at temperatures ranging from 10-18 °C, which will limit year-round use.  Managing and maintaining the biodigester is a tangible illustration of the carbon cycle, and a proof of concept about some agriculture circular economy initiatives.  Students will have opportunities to visit a larger demonstration project at a local university, and to compare the effort and efficiency of this energy production technology with another method of utilizing food waste, composting.  Figuring out the logistics of storing food waste, scheduling time to attend to the system, and planning to use the gas and byproducts, will all be part of the learning experience.  Evaluating this process and comparing/contrasting with composting will help guide our recommendations and information for our Bio-Energy toolkit.

Figure 2 picture of home scale biodigester, HomeBioGas 2

Biodiesel: what? how? pros/cons

They do say what goes around comes around. Rudolf Diesel invented the diesel engine in 1897. From the beginning, this engine could run on a variety of fuels, including vegetable oil. In 1900, one of the new diesel engines featured at the Paris Exposition was powered by peanut oil.”¹⁸

Biodiesel is made from any of various vegetable oils including used cooking oils, or animal fats. The process of converting vegetable oil to a useful fuel is called transesterification.  Adding an alcohol (methanol) and a catalyst (usually sodium or potassium hydroxide) converts the oil or fats into a biodiesel and glycerin.  Biodiesel can be made on a small scale, to demonstrate the technology easily.  One measures out the ingredients, mixes the alcohol with the catalyst, warms the oil slightly, mixes everything together well, and waits.  After the glycerin separates out and is removed, the biodiesel is basically ready.  Additional steps, called washing, where water is added to the biodiesel, stirred and let to separate again, will remove any residual glycerin and soap impurities.  On an industrial scale the process is more precise, but for school demonstration purposes, the resulting biodiesel will power an oil lamp, or could be mixed with approximately 80-90% fossil fuel diesel to power a diesel vehicle.  Maybe our program can source an old diesel van and convert it to run on fuel we make.

Biodiesel made commercially using vegetable oil, mostly from soybeans, must be grown on land that is then not being used for growing food or conservation efforts.  Another concern, which is true of all food-based bio-feedstock for any biofuel (such as corn kernels used to produce ethanol, see below) is that it can lead to increased food prices.  There are so many subsidies for clean energy which can shift the economic incentives for farmers away from food production towards biomass production.   

Since biodiesel can be made effectively, albeit with more batch-to-batch adjustments, with used cooking oil, this fuel could be a way to reduce existing waste streams, and to capture energy that would otherwise end up in landfills.  But even using virgin oil for biodiesel reduces the total life cycle GHG emissions because carbon dioxide released from biodiesel combustion is offset by the carbon dioxide absorbed from growing the oil plants used to produce the fuel.

Bioethanol: what? how? pros/cons

Ethanol is an alcohol made by fermenting the sugars (carbohydrates) found in biomass.  Current ethanol production relies almost solely on sugars extracted from corn, sugar beets, and sugarcane. It is easier to make bioethanol with food grade feedstock, such as corn kernels rather than corn stalks.  While the stalks and stems have fermentable sugars, they are in the form of complex carbohydrates bound up with cellulose and lignin.  To be able to ferment the sugars, the biomass feedstock must be pre-treated with acids or enzymes, or in some cases fungi, to begin to break down the plant structure, to access the glucose. The lignin component, once separated from the rest of the biomass can be burned as a fuel for the ethanol production plants boilers.

The U.S. is the world leader in biofuel production – generating 47 percent of global output over the last decade. The ten-fold expansion in ethanol production in the U.S. from 2002 to 2019 has been driven by the Renewable Fuel Standard (RFS), a federal program that since 2005 has required transportation fuel to contain a minimum volume of renewable fuels.¹⁹ So far, that has largely meant corn ethanol. According to the Department of Energy, 98 percent of gasoline in the U.S. contains some ethanol, most commonly 10 percent, or E10.²⁰ 

The promise of ethanol production is “that with the right technology for making and using ethanol, the chemical and energy industries could break their reliance on petroleum and drastically cut their climate impact.”²¹ So far this has not been realized. These crops are being grown on farmland and are using the same industrial farming techniques utilizing fossil fuel fertilizers and fossil-fueled farm equipment. Transporting them requires still more fossil fuel to power trucks.  The distillation following fermentation requires heating fuel. And carbon dioxide is a by-product of this process. One study, which claims to be among the first empirical assessments of ethanol production, found that the production of corn-based ethanol in the United States has failed to meet the US Renewable Fuel Standard policy’s own greenhouse gas emissions targets. Their findings are that major technological and policy changes would be required to meet the targets and to achieve the sorts of environmental benefits of biofuel production and use intended by these policies.²²

If, instead of using food crops, ethanol production focused on agricultural waste, this process would become much more sustainable.  Cellulose, in the form of lignocellulosic biomass, is abundant in agricultural and forestry waste. Common agriculture waste examples include corn stover – the stalks, leaves, and husks left over after kernels are harvested, wheat straw, and sugar cane bagasse.

There have been major investments, and roadblocks to success, for lignocellulosic bioethanol production.  There were problems with feedstock logistics, plant design, need for more research, and government regulations.  These issues contributed to making it unprofitable to bring this technology on-line, especially with the increase in fracking, which brought the price of fossil fuels down.  Despite the disbanding, or sale, of many of the initial startups who had invested in these technologies, there is renewed interest.  Some industry watchers think that after decades of false starts, the global push toward net-zero carbon emissions is now poised to combine with an improved suite of cellulosic technologies to usher in a new era for ethanol.²³

There are several major companies pursuing these technologies in 2024, and we can follow their successes and challenges in real time.  It is a reminder that the science and technology do not always match up with economics or political will, and sometimes a good idea is ahead of its time, or not feasible at all.  Time will tell.

Since bioenergy or biofuels are part of almost all proposed pathways to reduce human caused GHG emissions to limit global warming to 1.5 or 2 °C, these technologies need to be explored.  Whether these biofuels are currently, or can be, sustainably produced is still an open question, and one that will be the heart of the work students will explore as they work on their contributions to an Agriculture can Reduce the Climate Crisis Toolkit.