[Alby]

Hi all,
       I can get 1 tonne of compost for £40 + delivery , but , comparing this price to buying bags of compo is difficult as they are sold in ltr bags ie 25 ltr.
      So...  how many 25 ltr bags would make 1 tonne of compost ??
  It was much easier by the cwt....... I know Im getting old 

    Alby

[Alby]

Cheers kriss, BUT , wouldnt convert from ltrs to tonnes , oh dear bring back the cwt 
Alby

[BostonInbred]

Compost is sold by volume and not by weight, this is because the bulk density of compost depends on many factors including whats in it and how wet it is.

Aquatic compost, for example has a lot of grit in it to stop it floating away, so it will be much heavier than Bulb Fibre, which is mainly shredder bark and coir, and is very very light.

I woudl suggest what you are being sold is 1 cubic metre of compost, not one tonne, and if they are trying to sell you a tonne, then you want to know either the bulk density or the volume.

I can tell you ROUGHLY that a pallet of multipurpose of around 40 x  70L bags can weight anywhere between 600Kg and 1300 Kg.

[penance]

I 'think' 1 litre is around 0.75 kilo depending on moisture content.

So, 1 tonne is maybe around 600 to 800 litres.

I think £40 a tonne is a good price.

[mumofstig]

Have alook here to see if it helps any further

http://chat.allotment-garden.org/index.php?topic=50619.msg600625#msg600625

[BostonInbred]

I 'think' 1 litre is around 0.75 kilo depending on moisture content.

So, 1 tonne is maybe around 600 to 800 litres.

I think £40 a tonne is a good price.

it can be as low as 400 kg/cum if its  bark/fibre and dry as tinder or as high as 1300 kg/cum if its got a grit and sand in it and is very wet. You need to know the volume to compare. Same applies with soil. A tonne of topsoil soil can be anywhere between 0.7 cu/m and 1.3 cu/m . This meant last year the average load size of a curtain side artic (which can take 26 pallets spacewise) was only about 22 pallets because of the weight , and in the winter the lorries were loading out sometimes as low as 16 pallets because it was all so wet.

It really is meaningless to  talk about weight in such products, you can only really go on the volume.

Just to illustrate, the dry bulk density of peat can be calculated from the particle density and water content of the peat. Raised bog peat and fen peat, on average, have a particle density of ~ 1600 g/litre. In late summer the pores of the peat usually contain 80% to 90% water. Using these figures, the dry bulk density can be calculated from the dry matter. An analysis of 330 peat soils showed  about 3 years ago showed that the dry bulk density can be obtained from the equation:

ρt = 10xTM - 7.2

where ρt is the dry bulk density (in g/litre) and TM = dry matter (%).

And that only applies to the peat in cumbria and scotland. Its different elsewhere.  :S  You then have to factor back in the moisture content of the compost mix (as it gets wetted up whilst being mixed) when finished and the proportional bulk densities of the other ingredients in ratio.

BUt to get back to the original point, £40 a cubic metre (if that what you are getting) isnt bad because there 14 x 70L bags in a cubic metre, and that works out at £2.85 a bag, or £8.55 for three bags and you frequently see 3 for £10 as an offer in garden centres. But then buying compost as loose bulk is always cheaper, thats why growers do it.

[Alby]

Right .............  borrowed a 120 ltr of general pupose compost and weighed it    it weighed 33k . Which means I would have to buy about 30 of these bags to equal the Tonne on offer....  £40 is very good I think 

            Alby

[BostonInbred]

Right .............  borrowed a 120 ltr of general pupose compost and weighed it    it weighed 33k . Which means I would have to buy about 30 of these bags to equal the Tonne on offer....  £40 is very good I think  

            Alby

well assuming it has the same bulk density as the stuff you wieghed. If its denser, you'll get less and if its lighter you'll get more.

30 x 120L = 3.6 cu/m btw. That gives you a bulk density of 277g/L. Its either very very dry or its mainly bark and coir.