A Swamp Gas By Any Other Name

About four years ago UC-Davis conducted a study, the purpose of which was to help a national fast food corporation find a way to reduce methane/natural gas emissions produced by beef cattle destined to become their hamburgers. Researchers determined that 60% of the methane was emitted from the mouth and nose of these animals – leaving the other 40% to be released from the other end.

These scientists determined that adding 100 grams of dried lemongrass leaves to each cow’s daily ration led to a 33% reduction of methane during the period of the experiment. Evidently, what goes on inside the cow’s rumen is quite similar to what takes place in a stagnant swamp.

Wikipedia says that swamp gas, also known as marsh gas or bog gas, is a mixture primarily of methane and smaller amounts of hydrogen sulfide and carbon dioxide. It is produced naturally within some geographical marshes, swamps and bogs.

Bovine methane emissions were also addressed by calculations at the University of Vermont. Workers there determined that with the right pasture, and a winter feed that simulates pasture, some Vermont farmers saw an 18% methane emission reduction in their cattle. Achieved nationwide, that kind of greenhouse gas (GHG) mitigation could account for almost three-quarters of the goal of reducing dairy industry GHGs by 25% before 2030 – a goal set by USDA and the Innovation Center for U.S. Dairy.

Another benefit is that milk from pastured cows is often several times richer in omega-3 fatty acids than milk from concrete-bound dairy cattle in feedlots.

Scientists working for France-based group Danone (makers of Dannon Yogurt) found that when cattle were on pasture in spring, they were healthier. When they added omega-3-rich grasses to their feed year-round, the cows not only released less methane, but they also produced about 10% more milk.

Still, there’s no question whether ruminants produce GHGs, particularly methane. But W. Richard Teague, Ph.D., a grasslands research ecologist at Texas A&M University, along with coworkers, proposed that with appropriate regenerative crop and grazing management, ruminants can reduce overall GHG emissions. When properly managed, this livestock class can increase soil carbon sequestration and reduce environmental damage. These scientists tested their hypotheses by “examining biophysical impacts and the magnitude of all GHG emissions from key agricultural production activities, including comparisons of arable and pastoral-based agro-ecosystems.”

Teague’s crew showed that, globally, GHG emissions from domestic animals represent 11.6% of total anthropogenic (human-caused) emissions. Here the predominant GHG was methane (CH4), the main gaseous byproduct of the ruminant belching mechanism. This figure compares to cropping and soil-associated emissions contributing 13.7% of the grand total attributable to mankind. The primary source of this latter breakdown is soil erosion, which in the U.S. is estimated to be 1.72 gigatons of soil per year. A gigaton is one billion metric tonnes.

Permanent cover consisting of forage plants significantly reduces soil erosion, and ruminants consuming only grazed forages, under appropriate management, result in more carbon sequestration than emissions.

Incorporating forages and ruminants into regeneratively managed agro-ecosystems elevates soil organic carbon. This type of pasture management improves soil ecological function caused by tillage, chemical fertilizers and biocides. Keeping carbon in soil enhances biodiversity and wildlife habitat. Teague’s team concluded, “In order to ensure long-term sustainability and ecological resilience of agro-ecosystems, agricultural production should be guided by policies and regenerative management protocols that include ruminant grazing. Collectively, conservation agriculture supports ecologically healthy and resilient agro-ecosystems, simultaneously mitigating large quantities of anthropogenic GHG emissions.”

Intensified agriculture continues to increase surface water runoff, soil erosion and siltation of reservoirs. Under the anaerobic conditions of anoxic (little or no oxygen) sediment deposits, emissions of CH4, nitrous oxide (N2O) and ammonia from water bodies collectively almost equals the quantity of emissions from cattle. The N2O and CH4 emissions generated by the disturbance of continued tillage, plus the erosion of soil organic carbon (SOC) from clay and silt clay loam soils, have been one of the primary sources of GHG emissions.

In addition to the negative impact of the increasingly industrialized production of crops, there has also been considerable degradation of rangelands, which comprise approximately 40% of Earth’s tillable land mass. With rangeland’s ecosystems comprising roughly 25% of potential carbon sequestration in our planet’s soils, their degradation elevates GHGs, reduces ecosystem services and increases desertification. Note: organic matter is approximately 58% carbon.

Many rangelands have been subjected to increasingly heavy grazing by livestock. This grazing mismanagement has depleted root biomass and carbohydrate reserves in selectively grazed plants, plus reduced above-ground biomass productivity. Other negative effects of poor grazing management include impoverished herbaceous plant communities, more bare ground, lower SOC reserves and increased soil erosion and compaction.

Collectively, over the planet, these changes have contributed to lower surface water infiltration, increased runoff, downstream flooding and reduced water quality. As with tillage agriculture, the sediments from eroded grassland soils also emit GHG when organic matter in sediments enters anaerobic waterways. It can be shown that as the health of the land declines, so does the health of livestock and the people dependent on livestock.

Powerful reminders of the detrimental impacts of many current industrial cropping and grazing practices are anoxic levels in lower reaches of the Mississippi, the Gulf of Mexico Dead Zone and the multiplying demise of North America’s pollinators.

What I find strangely ironic is that learned faculty members – tenured at my Cornell alma mater – preach that the use of synthetic growth hormones will increase milk production per cow, thus reducing the number of ruminant animals needed to meet the nation’s milk requirement. A smaller national dairy herd does mean less methane being belched and otherwise emitted. What these scientists, however, conveniently ignore is that most of these bigger and bigger dairy farms employ anaerobic manure systems, which arguably are some of the biggest methane emitters on the planet.