Seeds

[DaveK]

I empathise - my wife bought a HOTBIN last October - just before the coldest, longest winter we've had for ages. We also didn't have anything close to a full starter amount of material. The result is that when I 'took over' composting in March I emptied the bin and started from scratch. The compost wasn't nearly as horrific as I'd feared, so we used it as a mulch ... outcome was a large number of tomato seedings and a few courgette seedlings!

100 F is only about 38 C - around blood temperature so it certainly won't scramble proteins (and hence sterilise seeds). I think you need a bin at around 55 C - 60 C to kill seeds (equivalent to 'pernicious weeds') - so you're looking at 130 - 140 F

After I took over composting (making sure that I had enough for the starter load plus top ups for the next month) the result was a bin that had reached 60 C+ in a couple of days and that stayed at that temperature from then on as I continually fed it.

I've bought a basic small shredder (Screwfix: Titan Rapid Shredder 2500W (with an induction motor and quite quiet to boot!) @ £85 with rave reviews. I also got some awesome scissors for the small stuff and the cardboard) . I use the Titan to shred garden waste and to create wood chips from any branches I can get my hands on - the chippings are wetted and go into rubble bags for a 3 months and are then dried out and re-bagged to be used as cheap (ie free) bulking agent.

The result is that the bin temperature (using the long deep thermometer) hasn't dropped below 55 C in the last 3 months and has been at 60 C+ for most of that time.

[EnlightenedElm]

Unfortunately if you turn a composting heap which is operating at high temperatures, you will likely disturb the material and cause the transfer of heat away from the active layer where it is needed to help safely destroyed seeds.

In a HOTBIN, as you do not turn the contents of the unit, any weeds and weed seeds have a continued exposure to hot composting temperatures which ensures that the seeds are properly destroyed.

[Salexander]

I once carried out a weed germination on sieved compost from a compost heap that had got to a high temperature with several turnings, and the only seedlings to germinate were tomatoes. The seed coat must be resistant to heat. Hope that helps.

[EnlightenedElm]

Hi Neil,

You mention that the temperature of your HOTBIN has exceeded 100° - can we double check whether this reading has been taken in Celsius or Fahrenheit?

[Neil Shelton-Smith]

I have recently emptied my bin and distributed the contents. However, we now have a bed with thousands of young tomato plants!! Does the hotbin not destroy tomato seeds? The temperature has exceeded 100 degrees at times which I would have thought destroyed anything! Any ideas?
Neil Shelton -Smith