Which is greener, biofuels or diesel?
When writing my recent post on EcoCor, an interesting Passive House prefab company in Maine, I had some fun with the owner's choice of vehicle, given that Passive House is all about reducing energy consumption. I wrote at the time (and have deleted since from that post as not really relevant):
I thought it hilarious when EcoCor owner Chris Corson showed up in at the NAPHN conference in New York City in this, the the biggest personal vehicle I have ever seen ever. I suspect that just driving to a Passivhaus jobsite in it uses more fossil fuels than the house uses in a year. Really, if you are going to sell Passivhaus to a bunch of TreeHugger types, you had better show up in the front of a Tesla or a Biekfiet.
I meant it to be funny, but it in fact sparked a serious discussion in Twitter among people who were at the Passive House conference and others following TreeHugger and me on Twitter . Chris Corson responded by noting that his main mode of transportation is a Prius, but that he had a lot of stuff to carry to New York. He also noted that he runs his truck on 100 % biofuels.
This actually raised a number of questions, the most interesting being, are biofuels better than diesel? It is a subject we have covered for years on TreeHugger, but what's the latest thinking? According to the World Resources Institute, "any dedicated use of land for growing bioenergy inherently comes at the cost of not using that land for growing food or animal feed, or for storing carbon."
Roughly three-quarters of the world’s vegetated land is already being used to meet people’s need for food and forest products, and that demand is expected to rise by 70 percent or more by 2050. Much of the rest contains natural ecosystems that keep climate-warming carbon out of the atmosphere, protect freshwater supplies, and preserve biodiversity. Because land and the plants growing on it are already generating these benefits, diverting land—even degraded, under-utilised areas—to bioenergy means sacrificing much-needed food, timber, and carbon storage
Their researchers note that bioenergy is really inefficient, and that solar farms are better:
Fast-growing sugarcane on highly fertile land in the tropics converts only around 0.5 percent of solar radiation into sugar, and only around 0.2 percent ultimately into ethanol. For maize ethanol grown in Iowa, the figures are around 0.3 percent into biomass and 0.15 percent into ethanol. Such low conversion efficiencies explain why it takes a large amount of productive land to yield a small amount of bioenergy, and why bioenergy can so greatly increase global competition for land. Solar photovoltaic (PV) systems’ conversion efficiency—and therefore their land-use efficiency—is much higher. On three-quarters of the world’s land, PV systems today can generate more than 100 times the useable energy per hectare than bioenergy is likely to produce in the future even using optimistic assumptions.
The two main biofuels used in North America are soy, turned into biodiesel, and corn, turned into ethanol. According to Jeremy Martin of the Union of Concerned Scientists, the use of soy for biodiesel is leading to significant imports of vegetable oils for biofuel production in America.
Biodiesel is made from all sorts of different sources, ranging from used cooking oil — which converts a waste into a valuable fuel — to food-grade vegetable oil — which turns valuable food into less valuable fuel. Unfortunately, despite encouraging growth in the production of waste-based biodiesel, the majority of the expansion is coming from soybean oil — causing the problems detailed in the infographic below, [see larger version here] and which does more to drive palm oil expansion and deforestation in Southeast Asia than increase planting of soybeans in the U.S.
Andrew Steer and Craig Hanson of the World Resources Institute conclude:
One of the great challenges of our generation is how the world can sustainably feed a population expected to reach 9.6 billion by 2050. Using crops or land for biofuels competes with food production, making this goal even more difficult. The world’s land is a finite resource. As Earth becomes more crowded, fertile land and the plants it supports become ever more valuable for food, timber and carbon storage—things for which we don’t have an alternative source.
The consensus among the Passivhaus experts was that if you need to drive a big truck, then perhaps one should just stick to conventional diesel, unless you are close to a good source of deep fryer oil.
Another option is to do what Greening Homes, the contractor who did my recent house renovation does, although it can get expensive.