“If we control methane, which is viable, then we are likely to soften global warming more than one would have thought, so that’s a very positive outcome,” says Dr. Drew Shindell, a climatologist at the Goddard Institute for Space Studies of the US National Aeronautics and Space Administration (NASA).
This is indeed encouraging news. The Philippines can contribute to the reduction of methane emissions by optimizing its rice cultivation techniques and handling the rice by-products after harvesting. The country ranks among the largest rice producers, as rice serves as the staple food for approximately 80% of its population, according to the Asian Development Bank.
“Rice is a plant that grows best in wet soil, with its roots flooded,” explains L. Hartwell Allen, an American soil scientist at the Crops Genetics and Environmental Research Unit in Gainesville, Florida. “But flooded rice crops emit substantial amounts of methane to the atmosphere.”
Rice-duck farming
Rice farmers can reduce methane emissions from irrigated rice paddies by integrating duck farming into their agricultural practices. In this method, ducks are introduced to the fields once the rice seedlings are well-established, allowing them to forage without damaging the fragile young plants.
The movement of ducks through the water promotes the growth of multiple tillers in the rice plants, potentially increasing annual yields by about 10-15 percent. In addition, the ducks’ activity at the bottom of the paddy contributes to the reduction of methane emissions.
One practitioner of this method is James P. Longcob, the proprietor of JPL Farms located in Purok 4, Abaga, Lala, Lanao del Norte. “In an integrated rice-duck farming system, I significantly reduce my expenses on rice inputs. I no longer need to apply chemicals such as pesticides or herbicides, and I also do not require additional fertilizers,” said Longcob during a webinar hosted by the Agricultural Training Institute in Northern Mindanao, which was streamed on their Facebook page.
Alternate wetting and drying technique
One effective method for mitigating methane emissions into the atmosphere is the implementation of controlled irrigation practices. The Laguna-based International Rice Research Institute (IRRI) has developed a system known as alternate wetting and drying (AWD) technology.
AWD technology enables rice fields to undergo a drying phase for a specified duration prior to the introduction of irrigation water. According to IRRI, “This technology can actually save farmers almost one-third of irrigation water without sacrificing yield.” The systems reduces the consumption of farm inputs such as oil, fuel, and labor associated with the operation of water pumps.
In the AWD system, rice fields experience cycles of flooding and drying. The duration of the non-flooded state can range from one day to over ten days, according to IRRI. This method employs an “observation well” constructed from bamboo, plastic pipes, or other locally available hollow materials, with perforations made in the lower half of the tube.
Studies conducted at IRRI have shown that AWD technology can reduce methane emissions by about 30% or even up to 70%, depending on water usage and management of rice stubble.
Incorporating stubble and rice straw into the soil
“Globally, roughly 800 to 1,000 million tons per year of rice straw is produced, with about 600 to 800 million tons per year produced in Asia,” said IRRI. In the Philippines alone, about 11.3 million tons of rice straw are produced.
Unfortunately, Filipino farmers consider rice straw as waste as it has little or no commercial value. “Much of this is burnt in open fields or incorporated in the soil in wet conditions during ploughing,” says a policy brief paper published by the Economy and Environment Program for Southeast Asia.
A study headed by Cheryll C. Launio of the Philippine Rice Research Institute (PhilRice) found out that early incorporation of both stubble and straw into the soil is “the most cost-effective way of disposing rice straw.” More importantly, it can help reduce greenhouse gas emissions, including methane.
Based on the five-year study (from 2006 to 2010), it was found that incorporating stubble less than 30 days before crop establishment is responsible for the largest contribution of greenhouse gas emissions. But combining rice stubble more than 30 days before crop establishment and incorporating composted rice straw into the field “yielded the lowest cumulative levels of methane and nitrous oxide.”
Turning rice straw’s methane into clean fuel
In the past, attempts to profitably collect and use rice straw for clean energy have almost all failed. That’s being turned around by Craig Jamieson. “Rice straw is one of the world’s largest bioenergy resources,” he said.
Jamieson, who headed Straw Innovations (SI) Ltd., is the man behind the Rice Straw Biogas Hub, which make clean fuel from waste rice straw. The produced fuel is used for drying the grains and milling thereafter. Drying is the most critical operation after harvesting a rice crop. When rice is harvested, it contains up to 25% moisture.
“It is important to dry rice grain as soon as possible after harvesting – ideally within 24 hours,” IRRI explained. “Delays in drying, incomplete drying or ineffective drying will reduce grain quality and result in losses.”
But before drying, rice has to be harvested first. Here, the SI 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 is 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 husks, 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.
To produce methane gas (a direct substitute for diesel or kerosene in conventional dryers) in the hub, water is added with the rice straw.
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.
So much ado about methane
As a greenhouse gas, methane was not given much attention like the carbon dioxide. But in 2001, the Intergovernmental Panel on Climate Change (IPCC) considered methane as “one of the most potent greenhouse gases on Earth.”
“Methane absorbs heat 21 times more than carbon dioxide and it has 9-15 year life time in the atmosphere over a 100-year period,” says Dr. Constancio Asis, Jr., a recipient of the 2011 Norman E. Borlaug International Agricultural Science and Technology Fellowship Award.
The Journal Science reported that the atmospheric concentration of methane has more than doubled during the last 300 years and is increasing at an annual rate of about 1% each year.
“What has fueled the rapid rise of methane from an obscure trace gas to a major factor in past, present and future climate change?” wondered Dr. Gavin Schmidt, a research scientist at the NASA Goddard Institute for Space Studies and Center for Climate Systems Research.
Methane is a very simple molecule (one carbon surrounded by four hydrogen atoms) and is created predominantly by bacteria that feed on organic material. “In dry conditions, there is plenty of atmospheric oxygen, and so aerobic bacteria which produce carbon dioxide are preferred,” explained Dr. Schmidt.
An article written by William F. Ruddiman explores the possibility that methane emissions started to rise as a result of anthropogenic activity 5000 years ago when ancient cultures started to settle and use agriculture, rice irrigation in particular, as a primary food source.
“Rice is a plant that grows best in wet soil, with its roots flooded,” explains L. Hartwell Allen, an American soil scientist at the Crops Genetics and Environmental Research Unit in Gainesville, Florida. “But flooded rice crops emit substantial amounts of methane to the atmosphere.”
In fact, rice fields are one of the major contributors of methane in the atmosphere. “An estimated 19 percent of the world’s methane production comes from rice paddies,” admits Dr. Alan Teramura, a botany professor at the University of Maryland. “As populations increase in rice-growing areas, more rice – and more methane – are produced.”
