Energy | METHANE DIGESTERS
RANKING AND RESULTS BY 2050 (LARGE) #30
8.4 GIGATONS REDUCED CO2
$201.4 BILLION NET COST
$148.8 BILLION NET SAVINGS
RANKING AND RESULTS BY 2050 (SMALL) #64
1.9 GIGATONS REDUCED CO2
$15.5 BILLION NET COST
$13.9 BILLION NET SAVINGS
The same year Thomas Jefferson penned the U.S. Declaration of Independence, Italian physicist Alessandro Volta discovered methane gas. Intrigued by the flammable air rising up from muddy waters along Lake Maggiore, he captured some and recorded his findings from ensuing experiments in a series of letters to friend and fellow curious mind Carlo Campi. “No, sir, no air is more combustible than the air from marshy soil,” Volta wrote on November 21, 1776, beginning to fathom the connection between the gas and the decaying vegetation. He went on to engage the fiery power of methane in a pistol of his own design. But is was not until a century later that scientists came to understand that microbes were responsible for the creation of Volta’s combustible air. That microbial wisdom is now being used to manage the planet-warming methane emission s that arise from organic waste—creating clean energy in the process.
Agricultural, industrial, and human digestion processes create an ongoing (and growing) stream of organic waste. Around the world, people grow crops, raise animals, make foodstuffs, and nourish themselves. Every one of those activities creates by products, from residues to excrement. Even with best efforts to reduce, there no way around waste. Some spoilage, for instance, is inevitable. And, as the saying goes, shit happens. Without thoughtful management, organic wastes can emit fugitive methane gases as they decompose. Molecules of methane that make their way into the atmosphere create a warming effect thirty-four times strong than carbon dioxide over a hone-hundred-year time horizon. But that need not be the case. One option is to control their decomposition in sealed tanks called anaerobic digesters, which facilitate the natural processes Volta found along Maggiore’s marshy shores. They harness the power of microbes to transform scraps and sludge and produce two main products: biogas, an energy source, and solids called digestate, a nutrient-rich fertilizer.
… Thanks to a supportive regulatory environment, Germany leads the way among established economies with nearly eight thousand methane digesters as of 2014—almost, 4,000 megawatts of installed capacity in total. Their adoption is increasing in the United States as well. Their adoption is increasing in the United States as well, particularly as attention to methane emissions grows. Small-scale digesters dominate in Asia.
Additional emissions savings result from how a disgester’s versatile outputs are put to use. Those end uses tend to depend on the scale of production. At the household level, largely in rural and unelectrified areas in Asia and Africa, biogas is utilized for cooking, lighting, and heating, while digestate enriches home gardens and small agricultural plots. Importantly, biogas can reduce demand for wood, charcoal, and dung as fuel sources and therefore their noxious fumes, which impact both planetary and human health. When produced at industrial scales, biogas can displace dirty fossil fuels for heating and electricity generation. When cleaned of contaminants, it also can be used in vehicles that would otherwise rely on natural gas. On the solids side, digestate supplants fossil fuel-based fertilizers while improving soil health. In addition to reducing greenhouse gas, methane digesters reduce landfill volumes and water-polluting effluent, and eradicate odors and pathogens.
Around the same time Volta was combusting gas, the phrase “waste not, want not” came into fashion. The Latin root of the word waste, vastus, means “uncultivated.” The opportunity for digesting organic wastes is, indeed, largely uncultivated. In the face of an ongoing stream of animal and human excrement and organic waste from food production and consumption—and a tandem surge of energy demand—we’d do well to take the opportunity to waste not, want not to heart.
IMPACT: Our analysis includes both small and large methane digesters. We project that by 2050, small digesters can replace 57.5 million in efficient cookstoves in low-income economies, while large digesters can grow to 69.8 gigawatts of installed capacity. The cumulative result: 10.3 gigatons of carbon dioxide emissions avoided at a cost of $186 billion. – Excerpt from DRAWDOWN – ‘THE MOST COMPREHENSIVE PLAN EVER PROPOSED TO REVERSE GLOBAL WARMING’ edited by Paul Hawken