Hemp can be turned into fuel, and not just one kind. Depending on what you’re after and what equipment you have, you can make ethanol, biodiesel, or biogas from the plant. Here’s a look at all three routes.
Ethanol
Ethanol is an alcohol that burns as fuel. To make it from hemp, you start by growing and harvesting the plant, then process the plant material to extract its sugars and starches. Those sugars get fermented and distilled into ethanol. It’s the same basic idea behind corn ethanol, just using hemp as the feedstock.
Biodiesel
Biodiesel comes from the oil in hemp seeds. You extract that oil and use it as a feedstock, then convert it through a chemical reaction called transesterification.
Transesterification sounds intimidating but the concept is simple: it swaps the ester group of a compound for a different one. For biodiesel, it converts the fatty acids in hemp oil into usable fuel. It’s the standard method for making biodiesel from all sorts of feedstocks, including vegetable oils and animal fats, and it’s popular because it’s relatively simple, inexpensive, and produces a high yield.
Here’s how it works with hemp oil. You mix the oil with an alcohol, usually methanol or ethanol, plus a catalyst like sodium hydroxide or potassium hydroxide. Then you heat and agitate the mixture, which makes the fatty acids react with the alcohol to form esters. Those esters get separated out of the mixture, and what you’re left with is biodiesel.
Biogas
Biogas is a renewable gas you can burn as fuel, and hemp can produce it through anaerobic digestion. That’s a process where microorganisms break down organic matter without oxygen, releasing biogas, a mix of methane and carbon dioxide. There are several digester setups you could use, including batch systems, continuous stirred-tank reactors (CSTRs), and anaerobic sequencing batch reactors (ASBRs). Which one fits depends on your feedstock and your goals.
The hands-on version goes like this. Harvest your hemp and chop it into small pieces so the microorganisms have more surface area to work on. Put the chopped material into a sealed vessel along with water and a culture of microorganisms. The microbes break down the plant matter and give off biogas as a byproduct. Keep an eye on the temperature and pH to keep conditions good for the microbes, then collect the biogas and use it as fuel.
Three plants’ worth of possibilities from one crop. Whichever fuel you’re after, hemp can get you there.