Grass could tame global warming gases
Photo: Neil Palmer/CIAT
Brachiaria grass trials at the International Center for Tropical Agriculture's headquarters in Colombia
Scientists have been predicting that a growing demand for meat and dairy products will lead to more deforestation, which will increase the harmful carbon dioxide released into the atmosphere as pastures are expanded and more land is devoted to sowing crops to feed the burgeoning population of animals reared for their meat and dairy products.
More animals will also mean rising emissions of warming gases such as methane directly from the livestock, and nitrous oxide from the fertilisers, manure and other animal waste. Both these gases are extremely harmful as their capacity to warm the atmosphere is far greater than carbon dioxide.
“The problem is that today’s crop and livestock systems are very ‘leaky,’” G.V. Subbarao, a senior scientist with the Japan International Center for Agricultural Sciences (JIRCAS0), was quoted as saying by the congress organisers' press release. “About 70 percent of the 150 million tons of nitrogen fertilizer applied globally is lost through nitrate leaching and nitrous oxide emissions; the lost fertilizer has an annual estimated value of US$90 billion.”
Secrets in the grass
The mechanism is known as “biological nitrification inhibition”, or BNI, said Michael Peters, who leads research on forages at the International Center for Tropical Agriculture (CIAT), based in Colombia. CIAT is a member of the Consultative Group on International Agricultural Research (CGIAR) Consortium.
Peters told IRIN the grass belongs to the Brachiaria species commonly found in east and central Africa and is native to the region. Animals that consume the grass produce higher yields of milk and their manure emits smaller amounts of nitrous oxide.
"A maize crop grown after planting a certain type of Brachiaria grass produces a respectable yield while using only half the usual amount of nitrogen fertilizer..."CIAT scientists have also found that a maize crop grown after planting a certain type of Brachiaria grass produces a respectable yield while using only half the usual amount of nitrogen fertilizer, because more nitrogen was retained in the soil, thus reducing nitrous oxide emissions and nitrate leaching. According to the UN Food and Agriculture Organisation (FAO), the livestock sector accounts for 65 percent of the nitrous oxide emitted.
The extent to which the Brachiarias could reduce emissions in the case of crops and livestock “depends… on fertilizer applied”. But “BNI leads both to suppression of nitrification and reduced nitrous oxide emissions by 30 to 50 percent in pastures,” Peters said.
“Our work on BNI started with a field observation made by one of our scientists in the 1980s - back then it was nothing more than a dream,” said Peters. “But now it’s a dream with an action plan and solid scientific achievements behind it.”
There is no data yet on the specific reduction of nitrous oxide emissions delivered by planting the grasses ahead of crops such as maize. BNI research forms part of a larger initiative referred to as LivestockPlus, which aims to provide major benefits for the poor and the environment through innovative research on tropical forage grasses and legumes.
Other research has shown that deep-rooted, productive Brachiaria grasses can capture atmospheric carbon on a scale similar to that of tropical forests, and could be a further plus for climate change mitigation.
“Livestock production provides livelihoods for a billion people, but it also contributes about half of agriculture’s greenhouse gas emissions,” Peters explained. “BNI is a rare triple-win technology that’s good for rural livelihoods as well as the global environment and climate. It defies the widespread notion that livestock are necessarily in the minus column of any food security and environmental calculation.”
Mitigating in countries that matter
Though Brachiaria grasses originated in Africa they are now planted more widely in South America. Peters told IRIN that breeding lines produced by CIAT have been brought back to Africa but currently cover no more than 10,000 hectares and involve only a few thousand farmers.
Africa accounts for a small proportion of greenhouse gas emissions, including those from the agricultural sector, while developed countries like the USA and emerging economies in Asia, where agriculture is practised on a far bigger scale, are responsible for far greater emissions.
Peters says Brachiaria have a good adaptation potential over a wide range of environments, as long as they are tropical. “This can include southern USA and many parts of tropical Asia. In general, Brachiarias are easy to manage but improved management increases performance. They are good pasture grasses and therefore spread easily.'
Eminent scientists like Peter Thornton from the International Livestock Research Institute have also been calling for regulations for better management of animal waste in the developing world, which could reduce the emission of nitrous oxide.