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Best biochar for a garden, by the job you are doing

Updated: October 2026

'Best biochar' is a useless prize until you say whether the bag is for two houseplants, a compost mix, or a small vegetable bed. In this amazon.co.uk set the same stars are shared across sizes, a 10 litre title can mean 1.05 kg or 4 kg, and one listing's 10 litre claim sits next to a 280 g unit count. This page names a conditional pick for each of those jobs, using only the eight kept ASINs. The full table is the [biochar comparison](/hub/fertiliser-soil-and-bark-mulch/biochar). A qualifying purchase can earn a commission at no extra cost to you.

'Best biochar' is a useless prize until you say whether the bag is for two houseplants, a compost mix, or a small vegetable bed.

Our top picks

McMillan McMillan Biochar 10L

Best overall

McMillan McMillan Biochar 10L
5.4/10about £26.95
View offer
Invigortex Black Gold Activated Biochar Soil Amendment (1 Litre)

Rank 2

Invigortex Black Gold Activated Biochar Soil Amendment (1 Litre)
7.6/10about £7.99
View offer
Invigortex EarthCraft Blends Bio Char Soil Improver for Plants (40 Litre)

Preis-Tipp

Invigortex EarthCraft Blends Bio Char Soil Improver for Plants (40 Litre)
7.1/10about £33.98
View offer
On this page
  1. 1.Best for a first pot
  2. 2.Best for a compost blend
  3. 3.Best when you need more volume
  4. 4.What not to call a winner

Best for a first pot

For a first pot, the sensible buy is a 1 litre bag at £7.99, and between the two at that price Black Gold (B0FVN92T1F) is the clearer listing. The country of origin is the United Kingdom, the volume field says 1 litre and the unit count says 1,000 ml. The 4.6 rating from 16 reviews is shared with the 3 litre and 5 litre Black Gold ASINs, so it is one pool, not 48 reviews. EarthCraft's 1 litre (B0G94TNM3Q) is the same £7.99 and a listed 105 g. The shared 4.0 from 16 reviews describes a fine, dusty grade. That is a poor match for a kitchen repot. Neither 1 litre bag prints a pH. Pot volumes are worked through on biochar for pots.

Best for a compost blend

For a compost blend around a 10 litre addition, put EarthCraft 10 litres (B0G968RWQ3, £16.99, listed 1.05 kg) next to McMillan 10 litres (B0DBRNBWMD, £26.95, listed 4 kg) and choose on weight and wording, not on stars. EarthCraft is about £1.70 per stated litre and about 105 g per litre. McMillan is the only bag here that says pure wood, with 10 litres, 10,000 ml and 4 kg pointing at the same pack more closely than the other 10 litre row. The coverage sentence is two rates at once: one bag for 20 square metres of vegetable garden, or for 100 litres of soil. The star line is 5.0 from 2. Follow one of those coverage sentences rather than averaging them.
McMillan McMillan Biochar 10L

Testsieger

McMillan McMillan Biochar 10L
5.4/10about £26.95
View offer

Best when you need more volume

When 10 litres is not enough, EarthCraft 40 litres (B0G9656SKP) is £33.98 and 4.2 kg, about 85 pence per stated litre. The weight scales with the smaller EarthCraft bags. The bullet list of sizes names packs up to 30 litres and does not mention 40 litres. Dust and torn-bag comments in the shared reviews matter more when the bag is this large, so open it outside over a sheet. If 40 litres is too much, Black Gold 5 litres (B0FVMV7DSY) at £14.99 still shows a 1 kg item weight, and the volume field is blank. Order that title only if you will judge the fill when it arrives.

What not to call a winner

The Potting Pantry listing (B0H7K9HZ1C, £16.95) is not a 10 litre recommendation. The title says 10 litres, the model is TPP-BIOCHAR-1L, the unit count is 280 g and the weight is 310 g. A 5.0 from two reviews does not outrank a 4.6 from 16 once you care about sample size. No ASIN here is EBC-certified on the listing. The top pick in the comparison scoring is the Black Gold 1 litre listing, on agreement between its litre fields and the shared rating. Checks that apply to any sack are the biochar buying guide.

Common questions

Which bag is the best biochar for a few houseplants?
Black Gold 1 litre at £7.99, if you want UK origin on the listing, a resealable-bag line, and litre fields that match. EarthCraft 1 litre is the same price at a listed 105 g, with dust complaints in the shared reviews, so mix it outside. One litre is a trial, not a bed. Neither listing prints a pH, so ericaceous plants stay a separate decision.
Which pack is the sensible buy for a compost mix?
Compare EarthCraft 10 litres at £16.99 and 1.05 kg with McMillan 10 litres at £26.95 and 4 kg. Take EarthCraft when a light fine grade and the lower price per stated litre are acceptable. Take McMillan when you want the pure-wood line and the heavier listed weight, and pick one of its two coverage sentences. For more volume, EarthCraft 40 litres at £33.98 is the lowest price per stated litre in the set.
Which listing actually names the wood?
McMillan, ASIN B0DBRNBWMD. The listing says pure wood, granules and powder, made as a soil improver and described by the seller as a slow-release organic fertiliser. There is still no NPK. Every other kept ASIN leaves the feedstock unstated, including the bags that say organic or activated.
Should I avoid a bag that reviewers called coal dust?
Treat it as a handling and description risk, not as a laboratory identification. EarthCraft's shared reviews include fine black dust, a torn bag, charcoal marks, and at least one buyer who thought it was crushed charcoal with no added microbes. The RHS definition of biochar is about carbonising organic material with little oxygen, and a barbecue look does not by itself prove or disprove that. If you need chunkier pieces or a named feedstock, choose a listing that states them, or buy elsewhere.
Are specialist brands better if they are not in the table?
They are different products. Carbon Gold's improver is a blend with biology and a certification claim for that blend. Natural Charcoal's enriched mix is priced about £9.95 to £32.95 and quotes grams per litre for the blend, not for these pure-char rows. Use them when you want that recipe. Use this page when you are choosing among the eight amazon.co.uk bags.

Related pages

How to use biochar

Biochar

What to check before you buy biochar bags in the UK

Biochar for pots and houseplants, and how much to mix

Biochar vs compost and which one you actually need

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the eight amazon.co.uk listings in this set, captured for the 19 October 2026 scoring pass. No kept bag shows an EBC class, a Soil Association number, a pH or an NPK. RPS 366 is an England position for waste-code biochar, not a household rule for Scotland, Wales or Northern Ireland.

  1. RHS, biochar (retrieved 19 October 2026)
  2. GOV.UK, RPS 366 storing and spreading biochar (retrieved 19 October 2026)
  3. GOV.UK, LRWP 60 making biochar from waste (retrieved 19 October 2026)
  4. GOV.UK, check if your material is waste (retrieved 19 October 2026)
  5. legislation.gov.uk, PFC 3 soil improver (retrieved 19 October 2026)
  6. European Biochar Certificate (retrieved 19 October 2026)
  7. Carbon Gold soil improver (retrieved 19 October 2026)
  8. SoilFixer, biochar application rates (retrieved 19 October 2026)