August 2004 Newsletter

Winergy: Alternative Energy Opportunities from the By-Products of Winemaking

By Eric Leber, Heritage College

For the past couple of years, students and faculty at Heritage College (Toppenish, Washington) have been pursuing beneficial uses for the nearly one-million tons of residual biomaterials generated every year by agricultural practices in and around the Yakima Valley.

Among the byproducts under consideration is "pomace," the 150,000 est. tons of material discharged annually from local wineries and grape-juice production facilities. The seeds, skins, and stems that make up pomace can be converted into liquid, solid, and gaseous fuels.

Planting the seeds for renewable transportation fuels

After mechanical separation, the seeds are pressed to yield (at approx. 12% by weight) poly-unsaturated oils (primarily C18:2 linoleic, omega-6 essential fatty acid). While this oil can be burned directly in internal combustion engines (possibly resulting in some fouling or glazing over time), work at Heritage has focused on splitting the tri-glyceride molecule into cleaner-burning single-stranded methyl or ethyl esters. These "biodiesel" fuels can displace up to 20% of the gasoline used in 2-cycle or 4-cycle engines or, according to comparable studies done elsewhere with this high-cetane liquid, up to 100% of the petroleum-derived fuel used in diesel engines.

While these renewable liquid fuels are very attractive from performance and environmental perspectives, at approximately $10/gallon to produce, they are less attractive from a business perspective. Considering that these seed-derived oils have two or three times the lubricity of petroleum or mineral oils, a more attractive business prospect could be marketing them as friction-reducing fuel additives that improve delivered horsepower and extend engine life by reducing internal heating and wear. The following figure illustrates the increasing delivery of power by an engine that is increasingly lubricated by small admixtures of methyl ester in the gasoline.

Vinomers

In a similar effort to encourage reducing our dependence on foreign oil, through a wide range of organic syntheses Heritage students have demonstrated that these grape-seed oils, as well as those from cranberry and raspberry seeds, are quite "hot" from a polymerization perspective. That is, their relatively abundant double bonds readily engage in chemical cross linking to forge strong connections to the neighboring molecules in the biopolymer matrix. Accordingly, they can displace 60% or more of the petrochemicals used in making plastics.

Calories from the cake

The "press cake," the defatted ligno-cellulose discharge from the seed press, also has energy potential insofar as it can be pelletized and burned, yielding – per initial calorimetric studies – approximately 50% of the heating value of wood pellets. Many of the organic components of the press-cake pellets can also be volatilized to form a biogas for subsequent heat and power production. While Heritage has yet to perform a net-energy analysis of this biomass gasification process, the College's parallel collaboration with the Community Power Corporation (of Littleton, Colorado) and the National Renewable Energy Laboratory (of Golden, Colorado) examining pelletized spent hops from the Yakima Valley has shown that material to be an "…excellent fuel for the down-draft power gasifier."

According to Robb Walt, President of CPC, the fuel-gas produced by the spent hops pellets is made up of CO (16.3%), CO2 (10.6%), CH4 (3.1%), H2 (17.4%), N2 (52.6%) and O (0%).

With a Lower Heating Value of 5.048 MJ/Nm3 (128 Btu/SCF), or 88% of wood pellets.

Eau de vitesse

A fuel as well as an octane enhancer, ethanol can be obtained from several post-winemaking stages. Heating the red pomace immediately after it leaves the winery releases residual alcohol which can be captured through condensation, while residual sugars in the white pomace can be fermented for ethanol production (which Heritage generally recovers through vacuum distillation).

Heritage students are also looking into the bioconversion of the sugar-rich liquor remaining after the production of decorative papers ("grapers") from grape skins. Hydrolyzing the skins' polysaccharides as a precursor to paper making results in more simple sugars that are candidates for fermentation (into alcohols, ketones, and other useful chemicals) by yeasts and other microorganisms.

Conditioning with compost

The high temperatures (in excess of 500 degrees F.) generated during the composting of the pomace (temperatures that have caused several serious burns, led to multi-million dollar settlements, aggravated legal and financial liabilities for those associated with grape growing, use, or disposal, and provoked the State's Supreme Court to place pomace under the Hazardous Waste Management Act) can be harnessed for beneficial purposes.

Controlled aerobic decomposition takes advantage of the high heating value of the pomace (approximately 20 MJ/kg of dry material, a position between brown and black coal and greater than wood) and the nearly ideal N:C ratio of 1:30 (vs. 1:511 for sawdust or 1:128 for wheat straw) to accelerate the propagation and growth of the thermophilic microorganisms responsible for breaking down the pomace.

This fall, Heritage intends to translate these favorable attributes into particularly rapid and intense production of heat, water vapor, and soil nutrients…all vitally needed to support, for instance, the College's greenhouse operations through the cold and dry winter months typical of Eastern Washington.

In summary

This research, which – with a grant from Battelle – initially undertook the cultivation and use of rape (or Canola) seeds for energy purposes, is continuing under the auspices of a grant from the Economic Development Administration of the U.S. Department of Commerce to form the basis for new businesses and jobs by devising value-added products and processes using regional agricultural wastes. Original pomace studies were performed with materials provided by Washington Hills/Apex Cellars of Sunnyside. Recently established collaborations with B.R.B. Seeds of Prosser extend this work into complementary considerations of cranberry and raspberry seeds.

These studies – part of the College's EcoVino initiative "More Good from the Grape" – demonstrate the technical feasibility and, in some cases, suggest commercial feasibility for transforming the Valley's agricultural byproducts from environmental hazards to environmental enhancements and revenue reducers to revenue producers. Today's work could indeed be planting the seeds for responsible production of renewable energy tomorrow.