Why California is spreading waste on the prairie

A groundbreaking farm scheme in California has the potential to cancel out the state's entire commercial and residential carbon emissions - by using waste.

A collaboration between scientists and San Francisco's garbage disposal unit, the scheme turns food and yard waste into compost and spreads it into rangeland, i.e. grassland, pasture, scrub and chaparral. A study by UC Berkeley calculated that covering just 5% of California's degraded, grazed rangeland with half an inch of compost would remove an amount of carbon roughly equal to the CO2 released in providing the energy used by the state's homes and businesses in a year.

As the calculation includes carbon drawn down into the rangeland and a reduction in emissions from landfill, it promises to create an elegant, circular economy-style solution to the twin problems of waste and climate change.

It would be a mammoth effort

After eight years of small-scale trials, the scheme, which is part of a wider Marin Carbon Project, is now ready to be tested on whole ranches or batches of government-owned land. 'If we prove this out in the next two years, you could go for 5%,' Kevin Drew, San Francisco's Special Projects Zero Waste Co-ordinator, told Apolitical. 'It would be a mammoth effort, capturing the food and yard waste currently going to landfills and combining it with manure and trimmings, but that could create a lot of compost, enough to take a shot at the 5%.'

The science is comparatively straightforward: as every gardener knows, compost makes plants grow bigger. Their photosynthesis draws in carbon dioxide from the air and gives out oxygen. The bigger the plants, the more carbon they use. The new news is that applying compost just once kick-starts a cycle of increased carbon sequestration for a period the researchers estimate at 30-100 years.

To give a sense of the potential scale of this process, the amount of carbon in the atmosphere worldwide drops 2ppm after every spring. (The global level generally fluctuates around 400ppm and the level considered safe by climatologists is under 350ppm.)

Drawing carbon out of the atmosphere - rather than reducing emissions - is attracting increasing interest as a means of preventing climate change. Norway has given out billions of dollars in subsidies to countries like Brazil to encourage tree planting. And France has launched a campaign to increase the amount of carbon in its soil by 0.4% every year from now on.

In California, the biggest agricultural producer in the US, drought and deteriorating soil quality have driven forward the idea of composting. Governor Jerry Brown has also launched a $20million Healthy Soils Initiative, which aims to incentivise farmers to adopt techniques that foster carbon sequestration and improve soil quality.

We believe we may have found a solution

The collaboration between the researchers and public servants on this project came about because the scientists were looking for a ready source of compost, and San Francisco has the most extensive composting system in the country, perhaps the world.

The state currently landfills over 12million tons of organic waste - not including waste from agriculture or sewage treatment - annually and has just passed legislation making it illegal by 2025 to dump organic matter into landfill. Instead the state will build or expand up to 200 composting facilities. 'These two policies are done in sync,' said Kevin Drew, 'because we're forcing the material out of the landfill, 1) to stop methane generation and 2) to create the feed stock for composting.'

The state has not yet committed to using that compost in this way and currently sells its compost for agricultural use. Drew said, 'We're not ready to say we're betting the farm on it, but we believe we may have found a solution that not only helps with climate change and builds healthier soil but also keeps farmers in business.'

There's this thing, a straightforward process, and it's a miracle

The estimated size of California's rangeland varies by definition but is in the region of 20million hectares, making the most immediate hurdle financial. On the small scale tested so far, the composting cost around $600/acre. At that rate, spreading compost on 5% would cost in the order of $100million - something the project hopes both to lower and to mitigate through federal subsidies. Supporters, however, argue that even at this rate it would be a cost-effective means of reducing greenhouse gas levels.

Moreover, those involved with the project are keen to avoid appearing to over-promise. Sources at the project emphasised to Apolitical that the process is still being developed and that the figures for carbon benefits are scientific estimates and cannot yet be precisely defined.

Nevertheless, there is a lot of quite hope that this simple process will bring unprecedented change. Kevin Drew said, 'I've been at this for 30-something years and we're just getting down to brass tacks here after a lot of diddlydicking around. I've been talking to other cities about waste for years, telling them one part of the story. And now I can tell them: holy smokes! There's this thing, a straightforward process at the end of the chain that you can do with the materials you've aggregated. And it's a miracle. Compost, it completes the circle.'