An Exploration on Greenhouse Gas and Ammonia Production by Insect Species Suitable for Animal or Human Consumption

A cricket versus a cow sounds like the setup to a joke. But here is the actual finding: per kilogram of mass gained, mealworms produce roughly a hundred times less greenhouse gas than beef cattle. That number comes from a controlled experiment, with chambers, gas analyzers, and carefully weighed insects, run by Oonincx and colleagues at Wageningen University. Here is how they did it, and what it means. Start with the problem they were trying to solve. The livestock sector contributes up to eighteen percent of total anthropogenic greenhouse gas emissions when you count the full life cycle of animal products. That figure sounds abstract until you break it down by gas. Livestock account for roughly thirty-five to forty percent of human-caused methane emissions and about sixty-five percent of nitrous oxide emissions. Those two gases are what make the number so alarming. Carbon dioxide is assigned a global warming potential, or GWP, of one as the baseline. Methane’s GWP is twenty-five. Nitrous oxide’s GWP is two hundred ninety-eight. So when you convert everything into carbon dioxide equivalents, the livestock contribution balloons. Most of the methane comes from enteric fermentation in ruminants — the bacterial process in a cow's gut that digests grass and releases methane as a byproduct. Most of the nitrous oxide comes from manure and urine on farms. There is also an ammonia problem, separate from climate. Livestock are responsible for an estimated sixty-four percent of anthropogenic ammonia emissions. Ammonia drives soil nitrification and acidification, and it can indirectly generate more nitrous oxide when soil bacteria convert it. All of this together — the methane from ruminants, the nitrous oxide from manure, the ammonia — adds up to a sector with an outsized environmental footprint. That footprint is what prompted Oonincx and colleagues to ask: what if we farmed insects instead? To answer that question rigorously, they built an experiment around five species. Three are considered edible: Tenebrio molitor, the mealworm; Acheta domesticus, the house cricket; and Locusta migratoria, the migratory locust. Two were included for comparison: Pachnoda marginata, the rose-ringed beetle larva, and Blaptica dubia, the Dubia cockroach. They housed the insects in open-circuit climate respiration chambers, each chamber eighty by fifty by forty-five centimeters, for a total volume of two hundred sixty-five liters. They ran each species through three to six repetitions over three days each. Air was drawn continuously through the chambers and analyzed on the way out. Carbon dioxide and methane were measured every nine minutes using infrared analyzers. Nitrous oxide was sampled by syringe at twenty-four, forty-eight, and seventy-two hours, and run through a gas chromatograph with electron capture detection. Ammonia was measured twice daily using gas detection tubes. Feed and substrate were also tested independently without animals, so the team could separate insect respiration from background emissions. Average daily gain, or ADG, the percentage increase in body mass per day, was calculated from start and end weights over the three-day window. Now for the numbers. Carbon dioxide production per kilogram of live body mass per day ranged from nineteen grams for Blaptica dubia up to one hundred ten grams for Locusta migratoria. When you express carbon dioxide per kilogram of mass gained — the more meaningful production metric — insects ranged from three hundred thirty-seven grams per kilogram for Blaptica dubia up to one thousand five hundred thirty-nine grams per kilogram for Pachnoda marginata. Pigs, for comparison, come in at eight hundred sixty-five to one thousand one hundred ninety-four grams per kilogram mass gain. Beef cattle at two thousand eight hundred thirty-five grams. Four of the five insect species beat or matched the pig range, and all five were far below cattle. Methane is where the story gets sharper. Three of the five species — the cricket, the locust, and the mealworm — produced essentially zero measurable methane. Pachnoda marginata produced four point nine grams of methane per kilogram of mass gain, and Blaptica dubia produced one point four grams. Pigs produce one point ninety-two to three point ninety-eight grams per kilogram mass gain. Beef cattle produce one hundred fourteen grams. So even the two insect species that did produce methane were in the pig range or below — and cattle weren't in the same conversation. The near-absence of methane in three species matters enormously because enteric methane from ruminants is one of the heaviest line items in the livestock climate ledger. Nitrous oxide varied across species but stayed well below the pig literature range of one hundred six to three thousand four hundred fifty-seven milligrams per kilogram mass gain. Tenebrio molitor came in at twenty-five point five milligrams and Locusta migratoria at fifty-nine point five milligrams — the highest insect values — while Pachnoda marginata was just over one milligram per kilogram mass gain. Ammonia told a similar story. The three species that produced measurable ammonia — the cricket, the locust, and the cockroach — emitted between one and one hundred forty-two milligrams per kilogram mass gain. Pigs emit one thousand one hundred forty to one thousand nine hundred twenty milligrams per kilogram mass gain. Cattle even more. Insects were not just better; they were categorically different. Why? The answer is biological, and the authors lean into it. Insects are poikilotherms — cold-blooded. They do not burn energy holding a constant internal body temperature the way mammals do. That missing thermoregulatory expenditure is expected to make them more feed-efficient, and the average daily gain data support it. Average daily gain for the five species ranged from four percent per day for Pachnoda marginata to nineteen point six percent per day for Locusta migratoria. Pigs gain about three point two percent per day. Beef cattle gain zero point three percent per day. Insects are growing faster while emitting less. The paper interprets the carbon dioxide comparisons through metabolic scaling — Kleiber's law, which describes how metabolic rate relates to body mass. The relationship is expressed as a constant times body mass raised to a scaling exponent. For homeothermic mammals, that exponent is traditionally taken as zero point seventy-five. For poikilotherms, it ranges from zero point sixty-seven to one point zero, with arthropods clustering around zero point eighty-two. When you apply the appropriate exponents and express carbon dioxide per kilogram of metabolic weight, insects range from six to twenty-nine grams per kilogram per day. Pigs and cattle, calculated the same way, come out around forty-one and twenty-one grams respectively. The insects are metabolically leaner. The methane contrast reinforces the mechanism: the methane that insects do produce comes from methanogenic bacteria in their hindgut — but it operates at a fraction of the scale of ruminant digestion. Put the average daily gain and the emissions together and the picture is consistent. Insects grow faster per unit of feed, they release less carbon, they release almost no methane in several cases, and they release far less ammonia. Across all four gases, the direction of the comparison is the same. What Oonincx and colleagues measured here is direct, physiological emission — the gases coming from the animals themselves, in chambers, under controlled conditions. This is not a full life cycle analysis, or LCA. A complete life cycle analysis would need to account for feed crop production, fertilizers, on-farm energy, transport, processing, and land-use change. The authors are explicit about this: they frame their data as inputs for that future analysis, which at the time of publication had not been done for edible insects. The direct emissions data are, in their words, indispensable for building the fuller accounting. That framing is the right one. This study doesn't prove that insect farming solves the protein problem. It shows that on the direct emissions measure — the gases the animals themselves produce — insects compare favorably to pigs and dramatically favorably to cattle. If that narrow slice of the ledger already looks this different, a complete life cycle analysis could reshape the conversation about sustainable protein production. The experiment is careful, and the numbers are striking. A cricket isn't just a punchline to a question about cattle. It might be part of the answer. This lecture was created by ennepō. Go to https://ennepo.ai to Discover, Create and Follow the latest research in your field. Read when you can. Listen when you want to.