Did you ever imagine that radishes could be used to produce renewable energy? No one saw it coming. However, Dr. Stephanie Lansing and Dr. Ray Weil in the Department of Environmental Science and Technology are testing dairy manure and forage radishes to develop a new technology that could enable corn silage-based dairy farmers to reduce greenhouse gas emissions, nutrient runoff, and environmental impacts while producing a renewable biofuel.
BIODIGESTER- CUTTING-EDGE TECHNOLOGY
“A biodigester provides an oxygen-free environment for microorganisms to break down waste material and produce methane biogas as a by-product of these metabolic processes,” explains Dr. Lansing, a national expert on low-cost digester design. “The produced biogas is about 60 to 70 percent methane, and can replace “natural gas” used in our homes for heating and cooking, thus eliminating the need for propane and charcoal.” The product of this digestion process, which is rich in nutrients, but low in pathogens, organic pollutants and odor, can be used as a fertilizer for agricultural fields.
Worldwide, there are more than 40 million small-scale anaerobic digesters and over 20,000 medium to largescale digesters, located mainly in China and India. The U.S. has only 140 digesters in the entire country, with the overwhelming majority employed by largescale dairy farms. In 2007, Maryland had 663 dairy farm operations, of which 90% were classified as small to medium sized farms with less than 200 cows.
Rising concerns over the environmental impacts and water quality degradation resulting from improper manure management, has prompted Dr. Lansing and her team to design a cutting-edge, low-cost anaerobic digestion system intended for small and medium size farms located in temperate climates like Maryland. According to Dr. Lansing, “The system is a modification of Taiwanese plug-flow digester design, which is utilized widely for organic wastes in southeastern Asia and Latin America.”
THE RADISH -DETOXIFYING & REJUVENATING THE SOIL
The forage radish, also known as a Daikon type radish, is an Asian vegetable that is used as a cover crop. It was introduced to the northeast region of the U.S. in the year 2000 by soil scientist Dr. Weil.
Cover crops provide major environmental benefits, as they reduce nitrogen leaching by efficiently capturing and recycling excess soil nitrogen. Cover crops also alleviate soil compaction and dramatically suppress early spring weeds. Furthermore, harvest of the forage radish removes phosphorus from the soil, thus remediating phosphorus-saturated soils, common on dairy farms. “Dairy farmers are increasingly planting this tap-rooted cover crop after they harvest corn silage in August or September,” says Dr. Weil.
Dr. Lansing and Dr. Weil are studying for the first time the benefits of co-digesting radish with manure. “This combination of manure and radishes has never been done before in an anaerobic digester,” says Dr. Lansing. According to them, this novel practice should increase biogas production during the winter period when it is most needed. It will also provide safe removal of the nitrogen and phosphorus, previously extracted from the soil by the cover crop. “Farmers will be getting many benefits from planting the radish in addition to the energy from the digestion,” adds Dr. Lansing. “Recycling expensive nitrogen fertilizer, alleviating soil compaction, significant suppression of weeds, savings on herbicide cost; and, in Maryland, a subsidy payment for planting the cover crop, are just a few of the benefits.”
The team’s innovative low-cost digester aims to make digesters available in the future to a majority of small and medium-scale dairy farmers in the U.S. Seeds for the radish will cost $10 to $40 per acre, and the building of the biodigester will cost from $10,000 to $15,000, which is far more affordable than the million-dollar models currently marketed in America.