California demo produces first low-carbon, whole-beet ethanol

By Susanne Retka Schill | March 23, 2015

Results from Mendota Bioenergy LLC’s Phase I demonstration plant in Fresno County, California, arrived last week, and were quite favorable, reported project manager, Jim Tischer. “We’ve made the first whole-beet, low-carbon ethanol in the United States,” Tischer said. The developers now need California Energy Commission approval before moving on to Phase II, proving the process in larger reactors and with more complex equipment. Though the demo facility has a 1 MMgy capacity, Tischer said the initial production runs will be smaller, dependent upon the availability of feedstock. The Phase II demonstration is expected to run in mid- to late-summer, when the next crop of energy beets is ready for harvest.

Sugar beets are a familiar ethanol feedstock, particularly in Germany, but until now it has been produced from the standard sugar extraction process using steam. Mendota Bioenergy’s process sizes down the whole beets, warms them up and liquefies using enzymes. “We’re substituting enzymes for the slope diffusers and tower diffusers in the standard process that use a lot of energy,” Tischer said.

Initial carbon intensity scores, calculated for the California Low Carbon Fuel Standard, give whole-beet ethanol a low CI score of 22, Tischer added. Energy beets are showing agronomic promise, as well. A 25-acre field raised under drip irrigation for the demonstration facility this year yielded 52 tons of beets at 17 percent sugar content. That amounts to a 1,200 gallon-per-acre yield, which Tischer said is nearly 25 percent better than Brazilian sugarcane. Mendota Bioenergy energy beets are expected to compete well with forage crops and be a viable rotation crop with high-value vegetable crops such as canning tomatoes. 

The project, which was initially conceived as a 40 MMgy ethanol facility, has been “right-sized,” according to Tischer, to a 15 MMgy plant that would consume beet production from 12,000 to 15,000 acres. “With just-in-time inventory practices, and considering beets are 75 percent water, you want to have feedstock within 25 miles of the plant,” he said.

Reclaimed water from the beets will be used in the process, with excess water supplying nearby irrigated fields. Other features of the planned integrated biorefinery include anaerobic digestion of stillage and food wastes for CNG and gasification of almond tree prunings to produce 2 MW electricity, supplying 80 percent of the plants’ demand.

“We see this as a public/private partnership, in harmony with the state’s low carbon fuel standard that will bring down the carbon in the state’s fuel supply,” Tischer said. Financing the project will be the mountain to climb, he conceded, with one-third to one-half expected to come from farmers and investors, 25 percent from the pollution control financing board and 25 percent from other sources. “Our goal with the demonstration is to prove out the technology.”