SUSTAINABILITY  |  Read Our Commitment

Biochar - specification changes (from April 2023)

TonyC 13/04/2023

Biochar - specification changes (from April 2023)

Summary of changes

  • Biochar granules 0-8mm will change to 0-13mm from April 2023
  • Withdrawal of Biochar 0-2mm fine granules from April 2023
  • Biochar granule 2-8mm remain available

Why the changes

We have been working to transition biochar production from a small batch process into a high-tonnage continuous process. 

Every Kg of biochar sold helps to mitigate climate change. However, to make a significant dent in the UK carbon footprint, we need to produce significant tonnage and have widespread use by gardeners, horticulture and agriculture.  In the UK, the biochar industry has broadly accepted that we need to make over 100,000 tonnes of biochar per year. This is a monumental step up from today’s output of c1,000 tonnes per year. 

Using this amount of biochar requires ‘biochar for agricultural soil’. The case for using biochar on farm soil shows beneficial impacts on crop yield and soil health but it has to be economically viable for farmers.  We are working with our pyrolysis equipment supplier and an investor to deliver this “step change” in output.  As a result, the following changes are being made to our biochar product range:

Particle size changes

The 0-8mm granule grade is being replaced with the 0-13mm granule size

To optimise the process at scale, we have to utilise “industrial scale” equipment. One such item we need is a large trommel sieve. These trommels are supplied with 13mm (1/4 inch) grid screens as the minimum size. Finer meshes wear out quickly, break too easily and clog too often. Hence the change from 0-8mm to 0-13mm.

  • There is no negative impact on quality and end-user growth benefits.
  • The composition of a 0-13mm grade is approx.: 0-2mm 30%, 2-8mm 50%, and 2-13mm 20%.
  • Conclusion: the 0-13 mm grade is tested and works per 0-8 mm grade. 

Change in moisture content

Our new production method water quenches the biochar from 700C when it leaves the pyrolysis unit down to 20C just before bagging.  This removes issues with handling dust and removes the downstream fire hazard.

Quenching leaves us with damp biochar. Damp biochar is very difficult to sieve and grade. Based on our many tests, sieving is nearly impossible unless the biochar has less than 10% moisture. Re-drying ‘quenched’ biochar would take a vast amount of heat energy, so unless absolutely required, redrying should be avoided on sustainability grounds.

Dusty biochar has always been difficult to spread on soil in windy conditions. A damp biochar product is beneficial to the end customer because it needs to be wet before it becomes active in the soil. A damp biochar product is beneficial to the end customer. There are customers and uses where fine powder/granule is needed, but these are rarely soil-based. 

  • Conclusion: 0-13mm granule, will be supplied damp at approx 30% moisture

Impact on Pricing

A substantial part of the small pack cost is courier postage and packaging. We have seen dramatic increases in costs to deliver parcels and ship palletised goods as well as increases in energy and packing material costs. Our new production process is lower cost. On the smaller retail packs (5, 10, and 20 kg), we have decided to retain the price per litre for 2023. Bulk loose loads of 10-20 tonnes will see a substantial price reduction.

For clarity - there is more water in the new 0-13mm than in the old 0-8mm grade. We are NOT charging customers for the extra water in the new quenched biochar. We are using the same price per litre, but the volume (litres) in each pack is less, so the Price per Kg sack has fallen - see table: 

ProductUnitPack SizePack sizeBulk bag
Old 0-8mm granulesWeight, Kg10 Kg20 Kg~420 Kg

Volume, litres~28 litre~57 litre1200 litres (1.2m3)

Price sack£36.00£57.60£625.00

Price £/litre£1.29 / litre£1.00 / litre£0.52 / litre

New 0-13mm granulesWeight, Kg10 Kg20 Kg~650 Kg  +/- 100 Kg 

Volume, litres~ 20 litre

~ 40 litre

1200 litres

New Price£25.80/sack£39.99 / sack£625.00

Price /litres£1.29 / litre£1.00 / litre£0.52 / litre

Biochar - pricing by weight (Kg)  or volume (litres, m3, cubes)

Things you need to know: biochar absorbs water - lots of it! The general weights & measures legislation for absorbent products and endorsed by the Horticultural Society for garden products which vary significantly based on water content should be sold based on volume. Pop down the garden centre, you will notice that bags of compost are sold based on litres, eg 50 litres and 100 litres. This is all fine until we attempt to courier parcels and move products in lorries. The prices for haulage are based on tonnes because each van/lorry is rated by a maximum legal payload in tonnes - for example, 1.5t, 7.5t, 18t, 24t artic. A 24t artic load of dry biochar would be 70m3 or as little as 40m3 wet.  

Philosophically, no one wants to pay for water. Noting that we often do pay for water in our products (consider that your favourite soda/pop drinks like Coke are typically +90% water), when it comes to biochar for soil, there are benefits of using damp biochar (see above).

As a buyer, to compare prices, your need to know the volume and dry Kg of the product.  We advise all customers to ask the prospective supplier for the unit weight, unit volume, % moisture content and/or the dry bulk density.  Our table below illustrates the scale of differences:


Our biochar is made in the UK, from sustainable UK wood resources but wood resources that are uneconomic to recycle into items like pet bedding or construction boards. The SoilFixer team dislikes the term “waste wood”,  but from an Environmental Agency category, we will be using ‘waste wood’, specifically compost wood oversize.

Trusted By Customers