Humanity has relied on biofuels since first mastering fire. Until the Industrial Revolution peat, wood, charcoal, whale oil, and plant oils represented the biofuels of choice. Fossil fuels began with coal. Fossil fuel crude oil and oil byproducts were a 19th century technical achievement. The automobile and internal combustion engine turned gasoline, formerly a discarded byproduct of oil refining into a major energy source. Industrial societies became fossil fuel addicts while the rest of the world, largely agrarian, continued to rely on biomass to fuel fires to generate heat and energy.
Biomass continues to be a major source of fuel. But the major consumers of energy are fossil-fuel junkies and addicts and it is these economies that are rethinking biomass as a fuel source because oil and fossil fuels like coal are seen as finite and non-renewable energy sources. It’s not just about climate change. It’s about dependency on a resource that is becoming more difficult to access.
If industrial society in the 21st century is to ween itself from fossil-based fuels, then it needs to develop alternatives. What are these alternative biomass fuel sources? How economical will it be to use these to replace crude oil and coal? Do biofuels help us deal with global climate change by lowering our carbon footprint?
Biofuels and Climate Change
What makes biofuels attractive is the fact that one can argue they are carbon neutral. Unlike mined and refined fossil fuels adding carbon to the environment, biofuels are contained within plants that absorb carbon dioxide from the air as they grow and release the carbon when finally consumed as fuel. This means they are carbon neutral. By theoretically not adding extra carbon to the atmosphere biofuels are environmentally sustainable and non contributors to global warming.
But is that truly the case? What about the industrial processes needed to synthesize the fuel from the biomass. What kind of energy is needed for that? If you are burning natural gas or oil to make biofuels then it is hard to claim that biofuels are carbon neutral.
EROEI as a Measure of Biofuel Effectiveness
Any time it requires more energy to produce a source of energy than the energy you get out of it one should pause and consider the implications. EROEI stands for Energy Return on Energy Invested. Here’s a handy chart that was inspired in part from an article I read, “Getting a Decent Return on Your Energy Investment,” written by Dana Visalli in 2006. The list includes conventional and unconventional energy resources and I must add that not all “experts” agree with these EROEI values or even what makes up EROEI calculations.
- Hydrogen EROEI of 0.5:1
- Corn Ethanol EROEI of 1.2:1
- Oil Sands EROEI of 2:1
- Corn Biodiesel EROEI of 3:1
- Geothermal EROEI of 3:1
- Switch Grass Cellulosic Ethanol EROEI of 4:1
- Solar thermal EROEI of 4:1
- Nuclear EROEI of 5:1
- Sugar Cane Ethanol EROEI from 8.3:1 to 10.2:1
- Solar PhotoVoltaic EROEI of up to 9:1
- Coal EROEI of up to 10:1
- Natural Gas EROEI of 10:1
- Hydropower EROEI of 12:1
- Wind EROEI of 19:1
- Oil Conventional EROEI currently estimated average 25:1 but declining
Food Crops As Biofuel Sources
If this isn’t the craziest of all developments that have occurred in the last 20 years — ethanol and biodiesel from corn is more about subsidizing American farmers to grow far more corn than can be consumed as food within the North American market. The issue is what to do with the surplus? What started off as corn for corn flakes is now a trillion-dollar enterprise churning out corn byproducts in foods, pharmaceuticals, cosmetics, animal feed and industrial chemicals.
Does that make corn a good biofuel source? Let’s look at the numbers.
- In 2009 the United States harvested more than 333 million metric tons of corn.
- It takes an acre field of corn, yielding 7,110 pounds (3,225 kg) to make 328 gallons (1240.61 liters) of ethanol.
- That amounts to 26.1 pounds of corn for a U.S. gallon or 3.1 kg to produce a liter. For the most part, only the corn kernels are used in producing biofuels.
- If ingested as food the calorie equivalent would be approximately 3,280.
- The average recommended daily calorie intake for women is 1,940 calories per day and for men 2,550.
- So 1 liter of biofuel eats more corn than an average human being’s daily calorie requirement.
- EROEI for corn ethanol is 1.2:1 which means you gain very little net yield
- EROEI for corn biodiesel is 3:1 which isn’t much better
How far can you go on 1 liter of biofuel? Not very far and considering how many people on the planet ingest less than the 2,000 calories daily it is difficult to rationalize using a food crop for biofuel.
It is another matter if only waste from the plant was used in creating biodiesel. Since 2009 a number of companies and universities started experiments with stover, the name for corn waste. We’ll talk about stover when we address other biofuel plant sources.
Sugar Cane as a Biofuel Source
It would seem that sugar cane makes a bit more sense as a biofuel source than corn kernels. First of all it has a better EROEI. Also, we can all do with a little less sugar in our diets. But let’s take a closer look at this miracle biofuel resource.
Brazil is the largest producer of biofuel from sugar cane. In 2011 Brazil will harvest more than 500 million tons of sugar cane. From each ton of cane the harvesters recover 135 kilograms (60 lbs) of sugar. That same ton of cane can produce 75 liters (20 gallons) of ethanol.
Other than sugar and ethanol, how is sugar cane used as an agricultural product? The tops of the sugar cane plant are used as animal fodder. The fibrous residue, called bagasse, is used as a fuel source in sugar manufacturing, paper and fertilizer. Molasses is a byproduct of the refining process. Molasses derivatives are used in vinegar, cosmetics, pharmaceuticals, solvents and industrial cleaners, and food additives.
Sugar cane, therefore, seems less controversial as a biofuel source than corn kernels. But in Brazil, sugar cane is being produced on land cleared of rainforest, savannas and grasslands usually by slash and burn methods creating huge atmospheric carbon output and contributing to increases in CO2.
Sugar cane plantations in Brazil are large and heavily treated with chemicals to stave off fungi and insect, plant and animal pests. Harvesting techniques involve burning of the cane stalks and the release of more greenhouse gases. Also since the cane is cut to the root, the soil is exposed and subject to erosion with little carbon sequestration. As demand for biofuels increase sugar cane plantings displace food crops. In recent years Brazil has seen corn and black-bean production drop by 10% because of sugar cane. When weighing the pluses and minuses of sugar cane versus corn as a biofuel source all the above has to be considered. And it is not a pretty picture if we are considering this as a resource to reduce carbon emissions while weaning ourselves off fossil fuels.
Other Biofuel Plant Sources that are Not Food Crops
There are many plant sources to consider when looking for biofuel sources. There are always whales and other animal sources but our society generally looks upon such choices as being particularly inhumane.
By no means an exhaustive list, let’s look at 3 biofuel sources that don’t compete with food and may prove to be far less controversial than corn and sugar cane.
When corn is harvested the remaining stalks, leaves, husks and cobs can be used to produce cellulosic ethanol. There are many challenges to overcome before stover replaces corn kernels as a primary biofuel source but there is promising news on one front, the creation of enzymes that can digest the residue and convert it. In a recent article in Scientific American, Steven Ashley talks about a new fermentation process that renders ethanol from stover.
The good thing about stover is the mass that can be collected from a corn field is equal in tonnage to the yield from harvesting corn kernels. So the resource is quite abundant and inexpensive when compared to a bushel of corn.
The bad news is simply this. The cost of production, the loss of soil nutrients, the added fertilizer requirements, the loss of the resource as animal feed stock, all have to be factored into the overall cost. How does removing stover impact soil retention and quality? What will it do to field runoff and potential erosion? Agricultural researchers are experimenting to find what is just the right amount of stover to remove and when to remove it so that it doesn’t have a negative impact.
And after all of this will the EROEI be worth it even if it matches existing numbers for corn biodiesel and ethanol?
Since 2008 the U.S. Department of Energy has been funding a number of biofuel pilot projects using switchgrass with a goal to get a better resource than corn for producing biofuels. So far the EROEI for switchgrass is proving to be no better than corn. But it is believed that EROEI can be improved to approach 4:1.
What makes switch grass more attractive as a biofuel resource?
- It has a higher biomass yield per acre than corn. In many areas it can yield two harvests in one growing season.
- It requires much less water and less fertilizer to grow.
- It grows on marginal lands that are unsuitable for other agricultural production.
- It can be harvested using conventional haying equipment.
- It is a perennial, self-seeding, a good environmental habitat for native wildlife, and excellent for soil retention.
What challenges remain?
- No current processes are yielding EROEIs approaching 4:1.
- If switch grass is harvested regularly will long-term yields decline.
Everything you ever wanted to know about algae can be found at Oilgae, an industry site dedicated to making algae the biofuel resource of choice. Algae is not one type of plant. There are micro and macro algaes. Seaweed is a macro algae but it is micro algaes that represent the greatest potential for energy crops. What makes algae attractive over corn, sugar cane or switch grass?
- Micro algae can yield as much as 56,000 liters (15,000 U.S. gallons) of oil per hectare a year. That is a much higher yield than what can be obtained from field crops.
- Micro algae can be grown in lots of environments where traditional crops would never thrive.
- Micro algae can be grown under conditions which are unsuitable for conventional crop production.
- Micro algae is a carbon trap extracting CO2 from the atmosphere.
With all these positive things to say about algae why aren’t we ramping up production? Here are a few of the reasons why we are not.
- Consistency of product remains a challenge. Micro algae can easily be contaminated in open ponds. That’s why many pilot projects are in closed pond environments.
- Yields are highly variable as the industry tries to develop optimal conditions for maximum yields.
- The largest byproduct of the algae production process is water. With 1,000 parts of water to 1 part algae, that’s a lot of water.
- Bio-engineered algae represents a potential environmental issue should genetically altered species contaminate the natural world.