The potential for sustainable energy is all around us. The earth is simultaneously asking us to save it while providing us with the means to do so. And many of the most viable forms of sustainable energy come from natural resources and phenomena. There’s wind energy which we’ve been able to harness through wind farms and turbines. There’s solar energy which we’ve successfully utilized through solar panels. There’s also hydro energy which can be used to move a turbine and create electricity. There’s even geothermal energy where we’ve learned to harness energy made from the heat beneath the earth’s crust. Among the many sustainable sources of energy that nature has given us is plant energy. Let’s look at the future of biofuels.
Corn & Fuel
All plant matter is structured with a component called light-cellulose. This component holds the potential for renewable energy as it is abundant in nature. There are many crops, otherwise known as ‘energy crops’, which can be converted into biofuels. One of these crops is corn which produces the highest volume of the residue of all major crops in the United States. There are two types of corn grown in the United States- sweet corn and field corn. Sweet corn is the type of corn that is commonly found on our dinner plates while field corn is used to create feed for animals as well as more sustainable sources of energy like ethanol.
What is Corn Stover?
Corn itself can be converted into biofuel by grinding the corn into flour and fermenting it for a few days. There are, however, several corn components left in the field after the initial harvest. The corn leaves, stalks, sheaths, husks, shanks, tassels, silks, and cobs that remain in the field are referred to as corn stover. The cellulose sugars remaining in the corn stover can also be fermented into ethanol.
These excess pieces are now being considered as an additional source of energy. According to the Agriculture Marketing Resource Center, corn stover is the largest quantity of biomass residue in the United States. There are approximately 120 million tons of biomass residue available annually.
How is Corn Stover Converted to Biofuel?
The components of corn stover are roughly 70 percent cellulose and hemicellulose and 15-20 percent lignin. The cellulose and hemicellulose components can be converted into ethanol while the lignin can be burned as boiler fuel.
There are two main methods of converting corn stover into biofuel: biological conversion and thermochemical conversion. Biological conversion requires pretreatment, enzymatic saccharification, fermentation, and recovery. Thermochemical conversion involves two separate processes: gasification and pyrolysis. Pyrolysis oil, or bio-oil, is created when the corn stover is rapidly heated in the absence of air. The rapid heating process involves temperatures ranging from 400-600 degrees celsius. The bio-oil created in this conversion includes charcoal, hydrocarbons, and gases which can then be refined into biofuel. In the gasification process, however, the corn stover is gasified while hydrogen, carbon monoxide, and carbon dioxide within the gas are fermented into ethanol.
The Future of Biofuel: Benefits & Risks
The benefits to the conversion of corn stover into biofuel are fairly obvious. There are large quantities of a resource that could potentially satisfy a large portion of our gas needs currently going to waste. If corn stover can be harvested, it could potentially supply 23-53 billion liters of fuel ethanol which is 10 percent of total gasoline needs. It will also allow the farmers and companies that currently work to convert field corn into ethanol to get the most out of their crop yields, a huge benefit when thinking of the future of biofuel.
One potential setback in this area of production is that, although the fuel source being produced is sustainable, the plants themselves may use non-sustainable energy sources in order to harvest and create ethanol. Luckily there are companies like POET who will make their renewable fuel so that the whole process remains eco-friendly.
The biggest problem with extracting the corn stover is that the corn stover left over from a harvest provides some significant benefits to the soil. It protects the land from water and wind erosion as well as providing fertilizing nutrients that keep the soil healthy and ready for the next crop yield. Therefore, removing the entirety of the corn stover could cause lower soil organic matter or carbon levels or the loss of the soil quality entirely.
The theory, however, is that there is a certain level of excess corn stover in fields that is safe to remove without risking these environmental or soil quality factors. The challenge moving forward when looking at the future of biofuels will be to find and perfect the removal of the correct level of corn stover so that we can have the additional fuel benefits this energy source can bring to our society without the risk of ruining the field itself.