The MAF system is extremely simple, the result of long and carefully engineered development. Units consist of an electrically powered fan box with simple electronic controls, which pumps air through 4 15 metre poly tubes with holes for air distribution at precise intervals. The pipes are laid on the ground parallel to each other at 4 metre spacings, and the material to be composted is piled up on top. Each of these units is able to compost 500 cubic metres of material, powered by a 1.1kw motor which only operates 10-20% of the time. To put this in perspective, a household toaster can draw 2kw of power. This is a huge reduction in power usage from using two 150kw compost turners 12 hours a day. Our current best estimate is that we now use 87 times less power per cubic metre of compost per year with the MAF system.
The above figures take into account two more efficiency benefits over traditional windrow composting. First is the increase in the amount of compost you can produce per square metre. Windrows are generally 1.5m high and 3m wide, with around a 1m gap between them. MAF systems are 20 metres wide and 2.5 metres high with a 3m gap between them. This arrangement is much more space efficient and allows you to fit twice as many cubic metres of compost on each square metre of hardstand.
Not only do you have greater efficiency of space, you also have greater efficiency of time. Maintaining oxygen at about half of atmospheric levels allowed us to reduce the active phase of composting from 12 weeks with windrows to 6 weeks with MAF. This again means that we can double the amount of compost per square metre of composting surface. Between increased efficiency of space and time, it is possible to produce 4 times as many cubic metres on the same area of composting surface. Day to day labour requirements are also less. Apart from monitoring, MAF piles only need to be moved twice during the 6 week composting process to turn the outside edges into the middle instead of turning windrows every day. This leaves you extra time to invest in preparing the best possible mixes for the highest quality compost.
Even though we now have the capability, we aren’t yet producing at our new maximum. It takes time to source enough raw materials and build markets to reach our maximum capacity. The amount of supporting infrastructure (hardstand, water supply and so on) that we have invested in was built around windrow composting, and we are now over supplied. We are using the opportunity to innovate and try out new procedures, but the advantage for you is that you can either save on the investment in hardstand for a new development, or expand your existing production without needing to increase the amount of hardstand you have.
MAF also provides a remarkable level of flexibility and control over the composting process. We have used variations in the MAF settings to manipulate oxygen levels (you might not always want full oxygenation for some projects), raise and lower pile temperature, to conserve water, and also to evaporate excess water. You certainly can just use the standard settings and get excellent compost, but once you get comfortable there is a bag of tricks waiting to help you control parts of your process you’ve never been able to before.