The Berkeley Composting Method, sometimes called rapid composting, is possibly one of the most efficient ways of composting material quickly, and without much loss in organic matter. But what is it? And what are some of the benefits and negatives I've seen in its use over the years.
I first learnt about the Berkeley composting method in Costa Rica on a small farm called Finca Amrta as part of my Permaculture design course. Scott Pittman started the compost on our couples days and we were all given the responsibility to collect scraps from the kitchen and turn it every second day for the duration of our two week stay. By the end of the two weeks the pile, that had been green and leafy, was transformed into a beautiful pile of black hummus ready to go on the garden.
But what is composting? Depending on the method, most composting is done by micro bacteria that consume organic matter to produce hummus which makes up the organic levels in healthy soil and house the beneficial microbes that keep a garden healthy and abundant. For the Berkely composting method the bacterial are labeled thermophilic meaning they produce heat while reproducing and can survive at much higher temperatures than other bacteria and mycellium. But in order for them to reproduce these bacteria need three things: Air to breath, Food to eat, and enough Space to do so. The air is created by pockets in the compost made by chunky matter and turning. Food is made up of carbon and nitrogen rich material such as kitchen scrapes, leaves, straw, grass clippings etc. And space means that any good compost should be at least 1m³ in side, the ideal size for microbes in the middle build up the heat they need to out compete other micro organic life. On top of these three microorganisms also need moisture, like all life on earth, at roughly 40-60% this gives them room to breath and move.
Berkeley Composting Method
The Berkely composting method started with a paper by Robert Raabe, Professor of Plant Pathology at the University of California. They did experiments to determine the ideal ratio of carbon and nitrogen while reintroducing air and distributing food through turning. The process played with what is called the K Curve of Kinetic Curve which describes the growth rate of bacteria. The curve shows a steady growth as bacteria consume food around them before plateuing out on what is called the stationary phase where the population stabilizes before eating all remaining food and then dying off.
What Robert Raabe did was cause more food to become available during the stationary phase by turning the compost and mixing dryer outsides with the more microbial rich middle. The effect on the K-Curve is that the population makes another growth in population as they consume more food around them. By continually turning the compost and redistributing food the curve continues to grow and plateau and grow and plateau until all the food in the compost in consumed. What this means is that the compost also continues to get hotter and hotter, reaching as much as 77C°, pasteurizing the compost and killing many pathogens and weed seeds.
While this sounds very intense and scientific, what the Berkeley composting method does is break it down into a very simple to follow recipe that will result in a very successful and quick compost that is free of seeds and biologically rich.
- The step to any great compost is to collect your materials. The Berkeley composting method outlines two main ingredients: brown, carbon rich organic matter, and green, nitrogen rich organic matter. The ideal ratio is about 30:1 Carbon to Nitrogen but since every material has a different ratio inside them what I find easiest is to have twice as much brown in colour material to green.
- Once materials are collected its time to build the pile. What I've used on many an occasion is a section of wire fencing, anything over 3.5m by 1m tall will give you the needed volume of 1m³. Pick a location with enough space to take off the wire and rebuilt it slightly to the side for turning.
- With the fencing in place begin by giving the bottom of the area a good soak with water. This will ensure that the moisture in the pile doesn't get sucked up by the ground and eliminates watering as you turn.
- Begin layering the material in the circle, watering every couple layers to make sure everything is wet, but no more then say a damp sponge (this is called the Squeeze Test). What I like to do is layer two different brown materials, one green layer, and then water til everything is damp.
- When the pile is complete you can cover the pile to reduce water evaporation or encase of heavy rains, but if you live in the UK then its not necessary. The day you make the compost counts as Day 1.
- Three days later, on Day 4, you will do the first turn. Take off the wire fencing, rebuilt it next to it and then turn the compost into the new area. Unless the compost has dried out there wont be any need to water it again, but if it is dry then add just enough water to get it damp again. You should also notice that the pile is steaming slightly at this point.
- Now you repeat this every second day, giving the compost one day of rest between turns. So turn it on Day 6, Day 8, Day 10, Day 12, Day 14, Day 16 and Day 18.
- On the 18th day the compost should be dark in colour and hot to the touch. There shouldn't be any intact organic matter left and it should have a sweet earthy smell. At this point you can continue to turn if its still not one, adding water if needed, or you can give it a few days rest to bring down the temperature before turning it out onto the garden.
(optional) If you are producing organic matter during this 18 day process then you can layer them into the middle of compost each turn however you might then need to add a few extra turns to make sure they're broken down completely before use on the garden.
So what are some of the benefits to the Berkeley composting method? The most obvious benefit is how efficient this system is. To be able to turn organic matter into finished compost in 18 days is nothing short of a miracle for most gardeners. This means that, providing you have a large supply of organic material, you can be turning out literally tons of compost each year, very useful for when creating new garden beds.
The second benefit is how easy it is to set up and take down. I've done this method while WOOF'ing on farms and its always so simple to set up and make a couple tons of compost while I'm there. I've also done this method as part of builds where I was setting up raised garden beds across three weeks and at the end had freshly made compost ready for the new beds.
And thirdly, since this is a biologically rich compost it can then be used to make compost teas or organic fertilizers. The way this works is that as the temperature decreases in the pile the resulting hummus attracts spores from mycellium and other beneficial organisms which take up home in the compost and further breakdown any left over organic matter. On top of this, larger trophic species such as worms, pill bugs and slugs can also move in to further diversify the soil food web.
Day 18 of Bearpit Compost: last turn*; hotter then ever before (66.2C); veggies barely recognisable; deep black colour with more white flecks; smells of woodlands and compost; moisture still perfect; 25% volume loss from initial; going to turn it three more times and then let rest for two weeks before seiving it for the garden. #composting #bearpit #bristol #berkleymethod #hotcompost #permaculture #lloydrichardsdesign
So what are some of the downsides to the Berkeley Composting Method? The most noticeable downside is how much energy you have to put into the compost to speed this system up. Moving 1m³ of compost eight times can be a real strain on your back and if the weather is miserable a tough job to get outside and get on with. We therefore always remind clients to be mindful of their posture and stop turning if they are not feeling up for it. Another solution for this is to make other people do it for you, as a WOOF'er this was always the top job for the volunteers on the farm and something that you just had to get use to doing as part of the job.
The second downside is that it can sometimes be hard to find enough materials to meet the minimum 1m³ size. This means that unless you have other systems in your house, such as animal bedding or a high production veggie garden, then doing the Berkeley composting method might only be done once or twice a year with seasonal jobs. A solution to this might be to start outsourcing your organic waste input, such as coffee grounds from local coffee shops, or neighbours leaves/grass clippings. By finding other organic waste streams you can help reduce that that would end up in the landfill as well as help build healthy soil locally.
The last downside is that while turning the compost helps to speed up the decomposition it can also release a lot of the nitrogen from the finished product. While it doesn't deplete all the nitrogen in the compost what you will find is that plants may require more of this compost then say a slow compost. What you will find is that in hot compost methods there is more carbon retention in the finished product, so the amount you compost might only lose 20-30% of its volume while slow composting will see between 50-60% volume lose. Slow composting will produce a richer nitrogen fertilizer but will take much longer to produce and will make much less, while hot composting produces much more, quicker but not as rich. A solution that I've been working on in the UK is to add a second step to the finished compost by feeding it to worms in a vermicomposting system. The worms chew through the finished compost with ease and deposit worm castings, a super high nitrogen fertilizer, into the compost bringing up the value and nutrition for the plants.
Starting to fill the beds with a combo of pig, sheep and chicken bedding mixed in with hot compost, coffee ground and autumn leaves. Trying not to think about how much material I'm moving right now. #gardening #landscaping #raisedbeds #lasagnabeds #farm #manure #sheep #pigs #chicken #devon #england #permaculture #lloydrichardsdesign
What Robert Raabe and his team at the University of California have created is a highly efficient model for producing large amounts of compost quickly and easily. While this does take a lot of backbreaking work, the end result is a highly biologically active compost that is ready to use on your garden within three weeks of starting it. With the right system producing a lot of organic matter at a time, such as a veggie garden or a local community, this method is an excellent addition to the composting system in order to turn that waste into a beautiful and useful resource.
Eighteen days ago all this was green organic matter we pulled from the Bearpit gardens with @ediblebristol. It was green, seedy and very course. By using the Berkeley Hot Composting method I was able to turn it into beautiful black gold with a bit of graft and commitment to turns. Time to recycle some nutrients back into the garden ^^ #composting #bearpit #bristol #incredibleediblebristol #berkleymethod #hotcompost #permaculture #microbiotic #soil #recycle #lloydrichardsdesign