Are the nitrogen levels of finished bokashi reduced compared to untreated food scraps? Does bokashi waste promote aerobic composting and increased pile temperature?”
Thanks for your insightful questions.
Firstly, your question about nitrogen. The bokashi fermentation process occurs in a sealed bokashi bucket meaning that none of the nitrogen (or other elements in the food waste) can escape. So the nitrogen levels in the fermented bokashi food waste will be the same as that in the original untreated food waste. While the total amount of nitrogen does not change, the form can and often does change. For example, some of the protein is transformed into mineral forms of nitrogen during the bokashi fermentation process.
Secondly, how bokashi helps your aerobic compost pile. Fermented bokashi food waste provides a great source of food to the ecology within a compost pile. Adding bokashi promotes a large increase and activity of soil organisms. The bokashi pre-compost is often damper than the moisture content recommended for hot composting. Pile temperatures will likely not increase immediately, as the bokashi will need to dry slightly. During this time there may be pockets of anaerobic activity in your compost pile. But don’t worry, this is from the healthy bokashi anaerobic microbes.
This graph shows effects of bokashi compost on pile temperature with the main peak in temperature occurring after the first turning.
I can also vouch from personal experience that bokashi pre-compost is great for compost piles. My compost pile is absolutely teeming with life and materials are breaking down a lot faster since I have started regularly adding bokashi pre-compost to it.
Hope that is helpful. Please ask any other questions you have about bokashi composting.
Nicki and the Bokashi Living team
Nicki, what’s your rationale for adding bokashi to compost? Here’s my rationale against …
As any ecology textbook will tell you, the amount of energy input to an ecosystem determines its size. In organic growing, plants can only feed on minerals released by the soil ecosystem. Therefore the end goal of any soil feeding method is to feed, enrich and diversify the soil ecosystem.
The energy in food resides in its chemical bonds. When food waste decomposes, over half of the bonds are lost (if aerobic) or over three quarters (if anaerobic, like most domestic composting). Decomposition releases to air the majority of input energy and organic carbon as heat & CO2 (if aerobic) or as methane [CH4] & CO2 (if anaerobic). In contrast, bokashi fermentation loses almost no chemical bonds, especially not carbon bonds; rather it restructures them. Hence, bokashi is more than twice as efficient at delivering energy and carbon to the soil ecosystem.
Both methods should deliver similar amounts of nutrients. This is largely true, except that decomposition can lose some nitrogen, in ammonia gas; and in open composting systems it leaches nutrients onto uncultivated ground (an argument for not using fixed bins or heaps). Hence bokashi is a bit more efficient at delivering nutrients too.
Therefore, in adding bokashi to a compost bin rather than direct to soil, you are effectively letting more than half of its potential benefit, sometimes much more, leak away to air and to any soil under a fixed heap.
You might also think that the energy and carbon will be lost as soon as the soil creatures eat it, so who cares. But that would be to misunderstand ecosystems. Once they’ve got energy, they hang onto it as long as possible. Waste matter and dead matter are cycled around the soil food web.
If only there were a way to include all green garden waste in bokashi! …