This is the time of year when compost bins work hard. They swallow up garden rubbish almost before your eyes and, however much you put in, there’s always room for more. This is mainly down to heat. As the sun warms up the compost bin, the microorganisms that break down the rubbish work faster and they generate more heat while doing this. On a cool morning you may even see steam rising from an open bin.

At this time of year a standard composter in a sunny place generates temperatures between 30C and 35C. This is excellent: the hotter the bin, the sooner you’ll get good, usable compost.

Unfortunately, home compost units can never get hot enough to kill off weed seeds and pathogens. Only large-scale commercial operations can reach the 60C to 65C needed for that. But, treated well, home composters can achieve a steady 40C to 45C, giving finer compost three to six months earlier than a standard heap.

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These very rough figures vary depending on three things: the type of unit you have; where it’s positioned; and what compostable materials you use. You probably can’t do much about the first two factors, but, with a little care, you’ll increase the bin’s heat with the third.

I put green, sappy material and brown fibrous stuff in my compost bins – sappy weeds and grass clippings, and dry twigs and toilet roll inners. For best results, mix green and brown together, rather than layering them lasagne-style. The resulting damp materials provide ideal conditions for composting microorganisms.

You’ll achieve a hotter New Zealand box by turning the whole heap. I can only face this chore once a year, but there’s no doubt regular turning reaps dividends. Turning works with an NZ box because you have a two-year system, where you fill the first bay one year then cover it for another year before using it. You fill the other bay during the second year.

Don’t turn small plastic compost bins that are topped up continuously, where after a year you remove finished compost from the bottom. You shouldn’t mix the bottom stuff with the fresh material. With these bins, simply stick a fork into the top 30cm to 40cm and shoogle it around to mix that layer together.

For a hotter working bin, mix in fresh grass clippings, assuming, of course, that you haven’t contaminated the grass with feed and weed chemicals. Put a thermometer into a pile of grass and it’ll register 60C in the blink of an eye – not for long, but enough to jiggle things up.

And, when you break materials down with a shredder, or even a rotary mower, you’ll turn up the heat. Plant debris often consists of thicker, slightly woody stems and leaves. When broken into small pieces, all chomped up together, the composting bacteria swing into action.

You may find composting seems to slow down, even in summer. If so, check out two things. Firstly, has the material become too dry? Composting bacteria and fungi only work if the material is damp. The sun and wind dry out the top or slatted sides of a New Zealand box. This can also happen to the corners of square and hexagonal bins. The solution is to pour a few buckets of water over affected areas.

Secondly, composting organisms live mainly in soil, so if the heap only comprises raw kitchen scraps, paper, card and garden prunings, you’ll need to throw in a few handfuls of topsoil, an excellent compost activator for any heap.