The Berkeley compost layer cake:
A guide to the biological engine in your backyard.
Some quick rules of compost:
- Compost is Aerobic decomposition. The bacteria, fungus and microbes breaking down your compost require oxygen!
- They also need nitrogen and carbon in the ratio of 1 part N to 30 parts C.
- Compost must be kept moist. Not too damp or there won’t be enough oxygen and not too dry or the microbes will die.
- Size matters. Bigger compost piles (over 1 cubic metre) will build up and retain much more heat, leading to more microbial activity, breaking down the pile much faster.
Get these right and your compost will smell lovely and break down quickly.
Guide to getting the ratios right:
- A one to one ratio of dry “brown” high carbon material and moist “green” high nitrogen material will result in the desired 30:1 carbon to nitrogen ratio.
- Layers make for a great consistency. It can be hard to make your pile completely homogenous so using alternating layers of high carbon and high nitrogen materials is a great compromise.
- Particle size is important. Chopping, shredding or even grinding up larger pieces will give more surface area for the microbes to work on. Watch that smaller pieces do not clog up your compost though, as a good flow of oxygen is required.
Recipe for a Berkeley Layer Cake:
- Start by laying out a square of straw 1m x 1m, and between 10 and 20 cm thick.
- Add a layer of high nitrogen material such as manure, 5 to 10cm thick.
- Add another layer of straw approximately 10 cm thick and wet the pile down.
- Continue to add layers between 5 and 10 cm thick of alternating high nitrogen and high carbon materials while continuing to wet the pile.
- When the pile is around 50 cm thick, place a stick in the middle of the pile to mark out the chimney. Continue to add layers around it.
- When the pile is 1m thick, remove the stick to create the chimney and the first stage is complete.
Completing the cooking:
- After about a week the compost will need turning.
- Peel the outer layers away and pile them in the centre of where the new pile will be.
- Fork the inner compost over on top of the least composted outer shell.
- Create a new chimney and leave it for another week to completely compost.