Would you eat bacteria to help reverse climate change?

Humans have long excelled at manipulating their environment to increase the amount of food an ecosystem produces, from burning underbrush to encourage the growth of berries or damming a stream to create a fishpond. The most extreme form of this survival strategy is crop agriculture, where people re-engineer an entire ecosystem to serve the needs of a few edible plants. Over the past century farmers have taken this strategy even further by using chemistry to enhance nutrient acquisition and pest control for our crops.

Under this system of industrial agriculture the production of cereal crops swelled from 800 million to more than 2.7 billion tons between 1961 and 2019, outstripping the contemporary growth in human population. But this success has come at a profound environmental cost. About half the world’s land surface is now used for agriculture, half of all biologically usable nitrogen is produced artificially, and 96 percent of mammalian biomass is that of either humans or our livestock. The result has been mass extinction and climate change, with agriculture responsible for about 25 percent of total global warming.

Ideas about how to reform agriculture to make it less destructive vary widely, ranging from organic farming and eating less meat to engineering crops genetically to make them more productive and less susceptible to pests. Replacing animals with lab grown meat is even on the table.

Over the past five years a more radical idea has emerged: growing hydrogen-oxidising bacteria for human consumption. These bacteria consume hydrogen for energy and carbon dioxide to make biomass. The plan is to combine the existing technologies of water electrolysis, bacteria fermentation, and atmospheric carbon dioxide capture to grow vast amounts of bacterial biomass using renewable electricity, essentially taking the strategy of ecosystem modification to its ultimate form. That is, humans taking over responsibility for capturing sunlight to split water and growing food in a completely artificially environment.

The resulting edible biomass is a protein-rich yellow powder that reportedly tastes like wheat. As George Monbiot reported for The Guardian in 2020, the substance could replace the feedstock necessary for animal agriculture or fillers in common food products; it could be the building blocks for artificial meat, milk, and eggs, or a substitute flour in pancakes or pasta.

This system of food production—generally called something like “Bacterial protein for food and feed generated via renewable energy and direct air capture of CO₂,” but which can more concisely be referred to as ‘bacilliculture’—has a number of advantages over traditional agriculture. Remarkably, even in its early stage of development, bacilliculture is far more efficient than agriculture at converting solar energy into usable calories. Consequently, feeding the world with bacilliculture would only require about 2 percent of the land currently used for crops. Likewise, the water required for bacilliculture would only be about 20 percent of that used for growing crops. While bacilliculture still requires the synthetic production of fertilizer, the bioreactor environment in which the culturing occurs would mean that nutrient run-off could be much more easily controlled. Commercialization of this technology is underway; Finnish company Solar Foods has promised a working factory by 2023.

What impact could bacilliculture have on climate change? As my colleagues and I explore in our recent study in Environmental Research Letters, the answer depends on several factors: How much of the global food supply will bacilliculture provide in the future? How reversible is agriculturally driven climate change? And finally, will bacilliculture be profitable enough to compete for a limited supply of renewable energy, and consequently what impact would that have on the effort to decarbonize the energy system?

The first question is the hardest to answer. It is possible that bacilliculture never catches on, or does so only for very special circumstances like long-duration space-flight, in which case it will have no impact on climate change. On the other end of the spectrum, bacilliculture could completely displace agriculture and become the primary food source for humans and domesticated animals. For the purposes of our study, we considered the latter scenario, because we wished to know the maximum potential of bacilliculture to impact climate change. Once the maximum possible impact is estimated, the actual impact will be some fraction of that.

Agricultural climate change is driven by the conversion of carbon-dense natural grasslands and forests into carbon-depleted fields and pastures, methane emissions from domestic animals and rice, nitrous oxide emissions from fertilizer, and the burning of fossil fuels to run agricultural machinery. Except for burning fossil fuels, these impacts have relatively short lifetimes: Land can revert to a natural ecosystem in the space of a few decades; methane lasts only 10 years in the atmosphere; and nitrous oxide breaks down in 130 years. So much of agricultural climate change should be reversible.

In idealized experiments we conducted using a global climate model, we found that if agriculture were suddenly abandoned in the year 2020, the warming effect from the non-fossil fuel component of agricultural climate change dissipated by half in 30 years and entirely in 250 years. In principle, then, widespread implementation of bacilliculture could reverse much of the agriculturally-driven climate change.

To explore the potential climate impact of bacilliculture in a more realistic framework, we modified the eight future scenarios used in the last UN report on climate change (IPCC Sixth Assessment Report) to account for 90 percent of agriculture gradually being replaced over the next century. These scenarios range from mitigation scenarios where the 1.5 degrees Celsius of warming is never reached, to scenarios where all known sources of fossil fuels are burnt. By year 2300, implementation of bacilliculture reduced warming by 0.05 to 1.0 degrees Celsius in these scenarios. The highest reduction in warming came from one of the mid-range scenarios where there is ambitious mitigation of carbon dioxide emissions but extensive expansion of agriculture. Four of the scenarios anticipate the need for net artificial removal of carbon dioxide from the atmosphere to achieve their temperature targets. In two of those scenarios, the temperature targets could be met without net carbon dioxide removal if agriculture is replaced in the late 21st century. Regardless of which scenario plays out, bacilliculture could make a nontrivial contribution to climate stabilization in the coming centuries.

The final aspect of bacilliculture that we considered was the potential competition between decarbonization and bacilliculture for renewable energy. Bacilliculture requires a lot of electricity, but the levelized cost of new utility scale solar power is now (in 2021) just 3.6 cents per kilowatt-hour and dropping. This means that the estimated cost for electricity to produce a kilogram of biomass from bacilliculture (about 40 cents) is similar to the market cost of soybeans (about 50 cents per kilogram). In fact, the latter are often compared with bacterial biomass because of their high protein content. We find there is a future economic scenario of low renewable energy cost, high grain prices, low carbon taxes, and high energy storage costs in which economically it would make the most sense to use renewable energy to produce food. This may not seem like such a bad thing given a quarter of climate change is from agriculture, but this is where the reversibility of agricultural climate change again becomes important. Prolonging the life of fossil fuel use creates climate change that effectively lasts forever, while prolonging agricultural sources of climate change creates climate change that can be mostly reversed in a human lifetime. That is, if implemented poorly, a transition to bacilliculture could make climate change worse by prolonging the existence fossil-fuel power plants.

The idea of eating bacteria is probably not particularly appealing to many. If bacterial biomass did become a wildly popular food, the high protein content and relatively low carbohydrate and oil content would limit how much you could eat each day without getting gout or other health problems, though in time these limitations may be relieved with genetic engineering. From today’s perspective, it seems likely that bacilliculture will only be deployed to fulfill its originally conceived purpose of feeding astronauts on long-duration space missions. Given these restrictions, why contemplate bacilliculture’s potential impact on climate change and the wider Earth system at all?

First and foremost, it is simply a professional duty to future generations. Predicting the future is hard, and the number of times that the implausible has become the inevitable with hindsight is too disconcerting to ignore. Once a new technology works at a small scale, envisioning and modelling its potential impacts on the Earth’s environment is an obligation for Earth system scientists. If we do our job right we can pre-empt terrible surprises, like the impact of chlorofluorocarbons on the ozone layer.

A second reason is that bacilliculture offers a potential way out of the mess humanity is in. As the Earth system buckles under the weight of climate change, pollution, and extinction, humanity faces the prospect of having to become planetary maintenance engineers with “the ceaseless intricate task of keeping all of the global cycles in balance,” as James Lovelock forecast in his 1979 book, Gaia. Bacilliculture is a possible solution for returning most of the Earth’s surface to a natural state and restoring the function of the natural biogeochemical cycles, while still being able to feed a global population of billions of people. It may only be dimly discernable now, but the vision of a future with Earth restored to its former richness and with everlasting freedom from hunger may be too alluring to resist.