Lowering Ethanol's Carbon Footprint with Energy Beets
The future of advanced biofuels is in beets. At least that’s the thinking of those behind Mendota Bioenergy LLC, a California energy beet-to-ethanol project that last year received an approximately $5 million grant from the California Energy Commission to build a demonstration plant in the Mendota area of Fresno County to test out its theory.
The project is in motion with the money being used to help turn 250 acres of beets into 285,000 gallons of ethanol per year, through advanced enzyme and microbial techniques.
Jim Tischer, project manager with Mendota Bioenergy, says the beet crop delivers ethanol yields that are greater per acre and have a lower carbon index than Brazilian sugar cane or North American corn. “This is an excellent re-establishment of an old crop to a new end, to make advanced biofuels,” Tischer says. “This is the first energy beet project to advance to the pilot and demonstration phase in the United States.”
If the pilot program is successful—and everyone involved expects it will be—construction of the nation’s first commercial-scale biorefinery in Mendota will begin with a 2016 target date. The goal of the commercial biorefinery is to produce 40 MMgy with about 15 percent of that production being cellulosic ethanol. That would put nearly 80 beet growers and 35,000 acres back into beet production.
Tischer says the biorefinery will also process waste pulp from the beets to produce biomethane for compressed natural gas, produce fertilizer and recycle water for irrigation. Based on projections, the biorefinery will create about 100 long-term jobs and 150 seasonal agricultural jobs and lead to millions of dollars of local economic activity.
Both the demo plant and the commercial plant would operate year-round and use beets grown by local farmers. Additionally, the plants would burn almond prunings and other wood waste to generate electricity for internal use and will convert some of those prunings into ethanol.
New Uses, Old Crop
Currently, nearly 95 percent of U.S. ethanol is made from corn but the renewable fuel standard (RFS), established by Congress in 2005, caps the amount of ethanol produced from corn at 15 billion gallons. That set the wheels in motion for the idea to use sugar beets for this purpose. After all, beets produce about 1,200 gallons per acre of ethanol, compared to 450 to 500 gallons per acre of corn.
Mendota Bioenergy LLC was created in 2011, but the idea harkens back a few years to when the Spreckels Sugar Co. plant closed and a dozen former beet farmers united to form the Mendota Advanced Bioenergy Beet Cooperative to seek out a new market for beets. They teamed up with agronomist Steve Kaffka and engineering expert Ruihong Zhang, both of the University of California-Davis.
Kaffka has a storied history of working on sugar beet crops and is considered a specialist on crop performance in the region. It’s his belief that the plan will be a success and he’s looking forward to the results of the pilot program. “My role in helping the growers is to advise them about the potential for the crops. I have been a member of advisory committees and know about a fair number of projects, but this has as good a chance as any of what I have seen of succeeding,” he says, “if beets can be produced profitably in the region and harvested or stored so they can be more than a short-season feedstock. What is really encouraging is that beet yields have been rising around the world fairly steadily over the last couple of decades and they continue to increase without increasing the inputs that are needed to produce them.”
“The introduction of energy beets will enable farmers to have another competitive crop in California and at the levels we think we can make the advanced ethanol, it should be a sustainable crop,” Kaffka says. “They grow year round, unlike other areas of the upper Midwest or Europe, they can grow in lower-quality soils (Class 2 or Class 3), they grow quite well with lesser quality water and they fit in well with rotations. What we’re seeing in tests is that beets may even fit in well with the canary tomato rotation, which opens up a whole new vista.”
New feedstocks and advanced fuels are essential if California is to meet the state’s climate change policies and reduce greenhouse gas emissions, says Robert Weisenmiller, chair of the California Energy Commission.
“The energy commission believes it is critically important to develop new feedstocks for the advanced biofuels industries and move away from reliance on a single feedstock crop like corn. The current drought and price spike for corn illustrates the risks of over-investment in a single crop feedstock for such an important component of our fuel supply in California,” Weisenmiller says. “We also need feedstocks with lower carbon content than corn. The average carbon content from Midwest ethanol just doesn’t move the needle enough in California to reduce the carbon content of our transportation fuels as laid out in our Low Carbon Fuel Standard.” For that reason, the CEC is investing in technologies and companies that can develop very low-carbon biofuels from waste-based and renewable resources, helping to create a more diversified portfolio of feedstocks and reducing the pressure on its farm systems.“The energy commission will continue investing funds in companies and technologies that will produce low carbon, sustainable fuel products for the next generation of vehicles that California will need in order meet our carbon reduction and emissions reductions mandates,” Weisenmiller says. “On the biofuels front, we want to take advantage of regionally available feedstocks. We don’t want to recreate the Midwest model of a monoculture feedstock feeding a single biofuels product. We want a variety, and we are confident that California companies will continue to work toward development of drop-in fuels that are compatible with modern engines and fully fungible with our existing fuel supply infrastructure.”
Mendota’s plan makes it a bellwether for the types of advanced technology, low impact, sustainable biofuels project that the CEC is helping to develop in the state.
“First, on net, this is nearly a carbon neutral and water negative project. Plus, it’s an integrated biorefinery, which means it has multiple processing loops to squeeze out the highest possible amount of sugar, starch and Btu from the beet and waste feedstocks,” Weisenmiller says. “It is a highly efficient project design. It will produce more clean water than it consumes by taking nonpotable process water from a neighboring operation and integrating it into the biorefinery.”
Mendota estimates the final fuel products will have very low carbon scores: 39.3 MMgy of ethanol with a carbon score of 17.6 grams of CO2 equivalent per megajoule (gCO2e/MJ) and 773,000 diesel-gallon-equivalent of biogas. The plan is to also produce 151,000 gallons of biodiesel from locally grown canola and used cooking oil.
“California sugar beets will use less water, fertilizer and pesticides than traditional corn cultivation for ethanol. There is tremendous cultivation expertise for this crop with the farmers and with the UC-Davis agronomy team,” Weisenmiller says. “Their goal is a 12-month cultivation cycle with yields of 40 tons per acre, which would translate to 1,000 gallons per acre.”
Energy, Water, Carbon
Tischer believes that one of the project’s biggest competitive advantages in the California market is that the initial energy-beet-to-ethanol carbon intensity rating came in below 20 gCO2e/MJ. When you compare that to the 58.40 gCO2e/MJ rating that the best Brazilian sugarcane ethanol and a carbon intensity rating of 80.7 for California dry mills using natural gas and producing wet distillers grains, the numbers are quite eye catching. “Until we produce it through the demonstration plant, which will start in February, we haven’t figured out how to do it,” he says. “UC-Davis indicates the carbon index will be less than 20 and the significance of that is the carbon index of gasoline is 85. Our plant will be one of the lowest in the U.S.”
Energy integration is a big part of the carbon score. As with any biorefinery, Mendota Bioenergy has a sizable energy component. Maximizing the use of the energy beets is obviously the primary concern, but the area surrounding the proposed plant also has a sizable almond crop. Plans include a biomass gasifier to convert almond prunings into steam and electricity, providing all the steam and 40 percent of the electrical power needs for the plant. “The gasifier means we do not have to burn coal [or natural gas] to make our process heat like some, which will keep costs low and keep the carbon index down. We’re also capturing the biomethane from an anaerobic digestion process and using that for transportation fuels.” The planned biodiesel production will be used by farmers in field operations to reduce their carbon footprint.
Another green aspect of the biorefinery is that woody plant matter, as well as beet pulp, will be used to produce about 15 percent of the ethanol as cellulosic at the Mendota plant. Also, the water in the beets will be captured during processing and recycled so that little fresh water will be used in the plant.
In California, water is a big factor that needs to be thought through in project planning. Depending on when the water districts were settled, some have surface water rights for the water that comes out of the mountains, while others have to pump it. “We had a short rain season last year, total precipitation was down, and it had an impact on crops,” Tischer says. “How that plays out in Mendota’s case is that three-quarters of the area we pull from has surface irrigation rights and they get water when no one else does. The other quarter is constrained by that. What that says is when we do our sourcing plan for beets (which looks to be 35,000 acres at this stage), we have to be sensitive to the traditional growing districts but also what the status is of water event districts. You may have to taper back, but you’ll still be in production.”
Mendota picked up its official contract from CEC on April 3 and is currently in the process of mobilizing its 34 subcontractors to move forward, with construction expected to begin in July and scheduled to be completed by December. “By mid-2014 we should have optimized the pilot plant and have a good idea if the turnout on ethanol from the energy beets is close to where we projected and if the economics will hold up,” Tischer says. “If that’s the case, we can move beyond the pilot plant to the commercial full-scale development and the 40 MMgy plant. Depending on where the finance community is, we could have the plant in operation towards the end of 2017.”
Author: Keith Loria
California-based freelance writer