Carbon-Neutral Activity & Biofuel

Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

New biofuels are often described as carbon neutral by their supporters. But what does it mean to be carbon neutral? And do biofuels really fit that bill?

What is Carbon-Neutral Activity?

The world is full of carbon. Life on earth is described as carbon-based. Our very bodies couldn't work without carbon. Carbon is the building block of everything from fossil fuels, to diamonds, to rocks, and plants and animals. So to an extent carbon itself is unavoidable. So what exactly do we mean when we talk about carbon-neutral activity?

Well, being carbon-neutral is more about carbon in a particular form: carbon dioxide. Carbon-neutral activity is any activity that releases no 'net' carbon dioxide into the atmosphere. Why does this matter? It matters because carbon dioxide is a greenhouse gas. Greenhouse gases are great, because they make our world warm enough that we can live here. Without them, we would be in real trouble. But human activities are pumping huge amounts of carbon dioxide into the atmosphere, and this is making the earth even warmer than it already is. Carbon-neutral activities are a way to stop this production of carbon dioxide, and reduce our impact on the world's climate.

There are many ways to make an activity carbon-neutral. Probably one of the least useful ways is to simply look at how much carbon dioxide your activities have produced in a year, and then plant an appropriate number of trees to counteract that. The only problem with this is that if everyone simply planted trees, we would run out of land on earth pretty fast.

So for an activity to be truly carbon-neutral it has to produce little to no carbon dioxide in the activity itself. For example, as a business you could power your entire operation using solar panels, recycle and compost every gram of waste your business produces, use electric transport, buy your electricity from entirely renewable sources, and then plant a few trees to make up for the resources used in building those solar panels. If every business attempted this kind of carbon-neutral activity, there would be plenty of space for that handful of trees each business would have to plant.

Tree planting helps offset carbon dioxide, but it is not an ideal solution
Tree planting helps offset carbon dioxide

Why it is easy to see how things like solar power are renewable, virtually carbon-neutral forms of energy, there are others that are more questionable. One example is biofuel. Let's take a look at biofuels in more detail, and try to figure out whether or not they are truly carbon-neutral as some people claim.

Solar panels are not even fully carbon-neutral because they take resources to make, but they are closer than almost anything else
Solar panels

Is Biofuel Carbon-Neutral?

A biofuel is a fuel produced from plant material, much like oil or coal. The difference is that oil and coal take millions of years to form, and so they aren't in any way renewable. Biofuels on the other hand can be created far more quickly. Examples include biodiesel and bioethanol. Biodiesel is a fuel made from rapeseed oil that can be used in diesel engines without having to replace or change the engine in any way. Bioethanol is a liquid fuel that is created from fermented sugar cane or wheat. It requires that an engine be modified before it can be used, but petroleum mixed with 10% ethanol will work in a regular engine.

Rapeseeds are used to create biofuels
Rapeseeds are used to create biofuels

So why do people claim that biofuels are carbon-neutral? If they're grown from plants, and the fuel is then burned, this doesn't seem particularly different from fossil fuels, like oil. Well, the difference is that the amount of carbon dioxide released when the fuel is burned is believed to be the same as the amount of carbon dioxide the plants absorbed when they grew. So replacing fossil fuels with biofuels should therefore reduce the amount of carbon dioxide released into the atmosphere.

Unfortunately, there's a problem with this picture. Producing biofuels is not just a matter of growing some plants. The process itself produces carbon dioxide. From the fertilizers used to produce the plants, to the transport of those fuels, to the processes carried out in production facilities, there are many costs, which mean the biofuels are not truly carbon-neutral.

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