[Yana]

Having done a quick look around, and chatting to the 'experienced' allotmenteers, opinion is divided as to whether you cover a compost bin or not. This includes when the bin is actively being filled and not just when full and being left to do the composting work for a while.
Those that use the Dalek type bins and some of the 'build-your-own from pallets' bins are covered whilst others are not. Those that are covered have carpet / black plastic / tarpaulin over them and are weighted down with bricks, pallets, other paraphernalia.
I have built a double-bin set up from pallets with one bin almost full and the other bin beginning to be used.
So do I:
Cover the bin(s) when full and leave to do their magic and make compost
OR
Leave the bin content exposed to the elements?

[arugula]

Daleks are obviously designed to work with the lid on, but as you say, you see different things going on with pallet bins. I'd tend to go for covering the full up pallet bins which are working away and leave open the one you are topping up. Other opinion will differ.

[Goosegirl]

I find the whole business so confusing. You need to let air in to make it work aerobically, but I have seen people tramping it down, which will exclude the air. Some bins are solid to keep the heat in, some made from pallets or wood-framed with gaps in the sides to let the air in, but then the heat gets out. Some are covered, some are not. An aerobic bin will rot down quicker. Methinks it is a combination of all these things. Covering it will keep moisture in and weed seeds out but you need to check it doesn't get dry.

[allotmentann]

I cover my wooden bins. I have been watching what happens to uncovered ones and as far as I can see the answer is - nothing. The stuff eventually dries out and the bin overflows, but no sign of any actual compost in any of them. Of course this is also because people don't shred or break down the stuff in the first place, don't add the right combination of browns and greens and don't keep the moisture right. I cover because I think it keeps it slightly warmer (and darker) and I water it if I think it is starting to get dry.

[sunshineband]

I cover mine while in progress for two reasons

- keeping in moisture

- keeping in heat

Makes compost so I am happy 

[angelavdavis]

I have a pallet composter which has fairly open sides (I do have split compost bags stapled to the sides but it isn't airtight) and an open top.  I cover any "working" compost with an old carpet to hold in the heat.  They are in full sun, so rot down really fast but I am conscious they are a waste of a good sunny spot!

I therefore had an idea and am planning to use half-pallets on top, lined with weed suppressant fabric and planted with strawberries next year though as partial lids for the bins, although will probably still use carpet or cardboard to hold in the heat.

[Yana]

What a great idea to use the space on top of the bins. I have foxes that enjoy eating the strawberries even though I  cover them with nets...... The foxes simply tear the nets. If I grow them up higher, maybe the foxes will leave them alone??

[Trillium]

I keep mine covered primarily because critters get in there and drag off tasty bits like empty egg shells, grapefruit rinds, corn leaves, etc, etc.  I'm fed up with the mess they leave in the yard so we've put a cover on with a heavy concrete block.

I too find uncovered bins dry out too quickly so once I've moistened things just right, the lid keeps them that way for ages. It also keeps the contents from getting overly wet with our recent rains and turning to sludge.

[angelavdavis]

What a great idea to use the space on top of the bins. I have foxes that enjoy eating the strawberries even though I  cover them with nets...... The foxes simply tear the nets. If I grow them up higher, maybe the foxes will leave them alone??

It's a possibility and worth a try if you can get hold of pallets cheaply or free Yana. 

The pallets I plan to use on top of the compost heap will fix into the sides, but leave half the top area free to access the compost, along with the front of the compost bin.  I plan to use this process: 16vxu0Q-ixM but use it horizontally. 

I intend to put it into place and fix it to the compost bins before filling with soil and planting.  This will be a winter/spring project as currently the half pallets are sitting under the large tomato pots in the greenhouse!

[jrko]

I use carpet to cover my pallet bin.  Keeps the heat in but allows water thru. 

The 1ft slow worm seems to like it.  He warms up underneath and then dives for cover when I lift the lid. 

[Markw]

I use old pallets, with black weed block stapled to the inside and clear poly on the outside with a six inch gap at the bottom to let the air into the compost more like a double glazed compost bin,and carpet for the cover and it works fine for me.