Text and Photos by Henrylito D. Tacio
A technology that can produce rice from harvesting to milling in less than a day is now possible. And its waste – rice straw – can be used in immediately drying the newly-harvested grains and then in milling them directly.
Thanks to Straw Innovations (SI), Ltd., which has established an industrial pilot plant in making clean fuel from waste rice straw. Now, it is teaming up with the Laguna-based Southeast Asian Regional Center for Graduate Study and Research in Agriculture (SEARCA) in a three-year project called Rice Straw Biogas Hub.
“Rice straw is one of the world’s largest bioenergy resources,” said SI Director Craig Jamieson in an exclusive interview. His work has taken him across Africa and Asia developing bioenergy solutions that enhance rather than compete with food production. “We want to showcase different ways to use it as clean fuel.”
A by-product of rice production at harvest, rice straw is perceived to have little or no commercial value. Unlike the grain’s cover (called rice hull), it is being left in the open field after harvest and standard combine harvesters are not designed to handle it.
Studies conducted by the Laguna-based International Rice Research Institute (IRRI) showed that for every 4 tons of rice grain about 6 tons of straw (called locally as dayami or uhot) are also produced, which are left in the open field. In the Philippines alone, about 11.3 million tons of rice straw are produced after every harvest.
Most Filipino farmers left rice straw in the open field and/or burned later. When left in the flooded fields, decomposed rice straw generates methane-emitting bacteria. Some of the produced methane is released into the atmosphere.
Burning rice straw, however, is not also a good practice. About 60%-80% of rice straw is burned, studies done by the Philippine Rice Research Institute (PhilRice) showed. Burning, they claim, is the most economic and efficient way of clearing the land for the next planting season.
But when done frequently, burning rice straw could reduce the soil’s nitrogen and phosphorus content by 25%, according to Evelyn Javier, supervising science research specialist of PhilRice’s Agronomy, Soil and Physiology division. “(Burning) also cuts potassium content in soil by 20% and sulphur by 5-60%,” she said.
More importantly, burning also causes air pollution as it produces carbon dioxide, carbon monoxide, nitrogen dioxide, and sulphur dioxide. Most of these are also classified as greenhouse gases.
Rice is the staple food for more than half of humanity. In the Philippines, rice is a staple food for about 80% of the population, the Asian Development Bank reports. The country is among the biggest rice producers.
Burning, including rice straw, is outlawed in the country. Several burning alternatives – like incorporating the straw into the paddy field, followed by alternate wetting and drying to reduce methane emissions – are recommended but not always possible. Growing rice on uplands is another option because straw can be incorporated into the soil without high methane emissions of flood rice fields, but it results in reduced yields.
In the past, attempts to profitably collect and use rice straw for clean energy have almost all failed. That’s being turned around by Jamieson.
“All around the world, the hunt has been on for a large amount of biomass that can be used for delivering clean energy without competing with anything else and we have millions of tons of it being burnt,” Jamieson was quoted in an earlier interview by World Biogas Association. “That’s a clear indicator that it’s there for the taking – a potentially vast resource that can be used for bioenergy and food production.”
The Rice Straw Biogas Hub is funded by Innovate UK under the auspices of the United Kingdom Research and Innovation organization. Also involved with it are UK SME Koolmill and UK academic partner Aston University.
The project is expected to make clean energy accessible to remote and underserved rural communities. “(It) will generate biogas as clean energy from waste rice straw and provide an innovative package of technology services for rice farmers,” said Dr. Glenn B. Gregorio, SEARCA Director.
The clean fuel is used for drying the grains and milling thereafter. “We asked farmers and their preference was to use the energy for productive purposes rather than domestic use. So, that’s what we are doing,” Jamieson told EDGE Davao.
According to Jamieson, his UK-registered group has established a rice drying service through the combustion of biogas from rice straw.
Drying is the most critical operation after harvesting a rice crop. When rice is harvested, it contains up to 25% moisture. The goal of rice drying is to reduce its moisture content to meet the recommended levels for sale, long-term storage.
But before drying, rice has to be harvested first. Here, the Straw Innovations Ltd. is introducing a rice harvesting system that it has developed over five years. “The main problems are in getting the rice straw out of the field and to a place where it can be used,” he said.
The solution: the 5-in-1 harvesting technology, referring to a machine, which is said to be the first of its kind in the world. “Our machine performs in one pass of the field and performs the five separate operations in conventional straw collection – harvester, chopper, rake, densifier, and collection. It’s more efficient and, critically, it works even in wet conditions (muddy or flooded fields),” Jamieson pointed out.
The collected palay are then brought to another machine where the grain is separated from the rice straw. “At the biogas hub, a dryer dries the rice grain with energy from the rice wastes, another removes the husk and another mills the grain to remove the brain, thus giving the final product,” Jamieson said.
The dryer takes about 12 hours for the grain to dry, Jamieson said. “The technology innovation is to use rice straw to power the process,” he said. “We give farmers the option to retain ownership of their grains throughout the process.
“In some of today’s cases, farmers only get 4% of the purchase price of rice. In our model, farmers can use our harvesting, drying, and milling services and then sell the finished products to the public. We just take our cut after the sale…”
To produce methane in the hub, water is added with the rice straw. The methane gas is a direct substitute for diesel or kerosene in conventional dryers.
“In the past, the government tried to give out free rice dryers but as soon as something broke, the dryers were no longer used,” Jamieson said. “Our business model is to own and operate our equipment and offer it as a service to farmers. They pay us a service fee but don’t need to buy or operate our equipment.”
During the process, the rice straw gets broken down into fertilizer, which can be used to fertilize the rice. Or, it can be applied as organic fertilizer for crops, vegetables and fruits. “It can be used for anything,” he said.
Dr. Gregorio said the Rice Straw Biogas Hub demonstrates efficient removal of waste rice straw from farmers’ fields and conversion into eco-friendly and commercially viable products, focusing on biogas and fertilizer.
“With this, it is envisioned that farmers could triple incomes while protecting the environment,” Dr. Gregorio stressed. “Through an affordable, value-adding commercial business model, farmers will avoid buying and maintaining expensive equipment.”
The clean fuel produced in the biogas is only used for drying rice grains. Because that’s what the farmers in the area need. Jamieson, however, said the fuel can also be used for cooking. “If that’s what those concerned farmers and communities want, why not?”
Jamieson believed the biogas hub can prevent the burning of millions of tons of rice straw as waste across the region each year. “The hub has exciting potential to bring clean energy access to the 150 million small-scale rice farmers who need it to process their crops and generate new income opportunities,” he said.
Dr. Gregorio is also very optimistic. “Rice straw biogas is an innovative way to increase our efficiency in producing rice and maximize the utilization of its by-products like straw for energy,” he said in an exclusive interview. “(It’s) a good example for a circular economy – nothing goes to waste. This is carbon-wise rice farming.”
Jamieson argued, however, that what his group is doing is not the only way to use rice straw for energy; it’s just showcasing one route among many. “Once we have harvested and collected the rice straw, the choice of end use will be site specific to some degree,” he pinpointed. – ###
