“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.” – Dr. Drew Shindell, a climatologist at NASA’s Goddard Institute for Space Studies, Columbia
University in New York.
***
Methane is the world’s second most important greenhouse gas and it is more potent than carbon dioxide. Thus, scientists are trying to figure out how the world can minimize the release of this gas into the atmosphere.
“If we cut methane emissions now, this will have a rapid impact on methane concentrations in the atmosphere and therefore on global warming,” contends a report published in theconversation.com.
Rice cultivation is a good start. Flooded rice paddies emit as much as 500 million tons of methane, around 20% of total man-made emissions of this gas, according to the Laguna-based International Rice Research Institute (IRRI).
Scientists explain that long-term flooding of the fields cuts the soil off from atmospheric oxygen and causes anaerobic fermentation of organic matter in the soil. During the wet season, rice cannot hold the carbon in anaerobic conditions. The microbes in the soil convert the carbon into methane which is then released through the respiration of the rice plant or through diffusion of water.
On the other hand, decomposition of organic material in flooded rice fields produces methane, which then escapes to the atmosphere during the growing season. “Traditionally, farmers flood their rice fields continuously and incorporate 4-5 tons of rice straw per hectare at land preparation,” says a report released by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD). “Every year, these practices release 5,883 tons of methane to the atmosphere.”
In Isabela State University, a study funded by PCARRD showed that by using simple science-based strategies, farmers can contribute significantly to the reduction of methane emissions. For instance, mid-season drainage of irrigation water reduced methane emission by 48%.
Meanwhile, composting of rice straw resulted in 64% less methane emission released in the air. By combining mid-season drainage and application of rice straw compost, methane emission is further reduced by 81%.
Rice farmers can also help reduce methane emissions into the atmosphere by adopting controlled irrigation or alternate wetting and drying (AWD) technology.
Developed by the Laguna-based International Rice Research Institute (IRRI), AWD is a technology which allows rice fields to dry for a certain period before applying irrigation water.
Also called controlled irrigation or intermittent irrigation, AWD technology can actually save farmers almost one-third of irrigation water without sacrificing yields. It also saves farm inputs like oil, fuel, and labor being utilized on the operation of water pumps.
In an 8-season field experiment conducted at IRRI, it was found that AWD “has real potential to reduce the global warming impact of paddy fields to one-third of the conventional continuously-flooded field water management.”
In a paper presented during the international workshop on “Water Management and Technology for Crop Production under Climate Change” in Suwon, Korea, the authors claimed AWD “can reduce methane emissions by over 40%.”
The AWD technology can be started a few days after transplanting (or with a 10-centimeter tall crop in direct seeding). When many weeds are present, AWD can be postponed for 2-3 weeks until weeds have been suppressed by the ponded water. Local fertilizer recommendations for flooded rice can be used. Nitrogen fertilizer may be applied preferably on the dry soil just before irrigation.
“A practical way to implement AWD technology is by monitoring the depth of the water table in the field using a simple perforated field water tube,” IRRI explains. “When the water level is 15 centimeters below the surface of the soil, it is time to flood the soil to a depth of around 5 centimeters at the time of flowering, from one week before to one week after the maximum flowering.”
The water in the rice field is kept at 5 centimeters depth to avoid any water stress that would result in severe loss in rice grain yield. The threshold of water level at 15 centimeters is called “safe AWD,” as this will not cause any yield decline because the roots of the rice plants are still able to take up water from the saturated soil and move it to the root zone.
“The field water tube used in this technology will help to measure the water level in the field so that incipient water stress in the rice plants can be anticipated,” the IRRI points out. As such, the AWD technology does not only save water but can greatly reduce emissions of methane.
In Zamboanga del Sur, farmers release ducks after harvesting rice. Nonoy E. Lacson, in a report, wrote: “Under the system, ducklings are released to rice fields to graze and feed. The paddling movement of the ducks in the rice fields increases the rice tillers, in effect raising annual yield by as much as 10 to 15 percent. Besides their paddling, ducks also eat the insects and unwanted weeds in the rice field.”
According to the agriculture department, the integrated rice-duck farming system represents one of the most effective methods for enhancing rice productivity, as it minimizes labor and input by eliminating the use of artificial fertilizers and chemicals. Transitioning from traditional planting methods that rely on inorganic materials to this innovative technology offers farmers an additional source of income and food.
This technology is ecologically beneficial as it reestablishes the connection between humans and nature. It constitutes a sustainable approach, aiding in the prevention of soil, water, and air pollution caused by harmful chemical substances that adversely affect both the environment and human health.
“The integrated rice-duck technology reduces the use of chemicals,” the agriculture department points out. “Since ducks are grown alongside rice paddies, they eat harmful pests at the same time their dung fertilizes the soil. Their paddling movement cultivates the soil and destroys the weeds. Its benefits to the farmers are immediately felt and tangible.”
Eating less meat is another way to curb the production of methane to be released into the atmosphere. “Meat production puts immense pressure on earth’s ecosystems,” The World Counts points out. “And global meat consumption is increasing non-stop.”
Cattle growing, for instance, is one of the most resource-intensive and environmentally impactful foods to produce. “Beef production requires four times more land (and four times as much greenhouse gas emissions) than dairy for every unit of protein consumed,” said the global food policy report.
Damian Carrington, writing for The Guardian, agrees. “The popular red meat requires 28 times more land to produce than pork or chicken, 11 times more water and results in five times more climate-warming emissions.
“When compared to staples like potatoes, wheat, and rice, the impact of beef per calorie is even more extreme, requiring 160 times more land and producing 11 times more greenhouse gases,” Carrington wrote.
Think globally, act locally, experts advise. Some scientists believe that eating less meat would be a better way for people to cut methane emissions. Or, as Prof. Mark Sutton, of the UK’s Centre for Ecology and Hydrology, puts it: “Avoid excessive meat consumption, especially beef, is good for the environment.”
