Spot trading of biomass and biomethane

A commodity market needs a unit. Oil has a barrel of a defined density band, wheat has a bushel at a defined moisture. Solid biomass has neither, and the reason is physical rather than administrative: what is being bought is energy, and the mass that carries it varies by more than the trading margin.

Moisture is the dominant variable

Freshly felled wood is roughly half water by weight. Air-dried wood settles near 15–20 per cent; a pellet made to ISO 17225-2 class A1 must be at or below 10 per cent. Water does not merely dilute the fuel — burning it costs energy, because the water in the feedstock has to be evaporated inside the furnace and the latent heat of vaporisation, about 2.26 megajoules per kilogram, is never recovered in a conventional boiler. So the net calorific value delivered per tonne falls faster than the dry-matter fraction does. Two loads of identical species and identical mass can differ by a factor of two in useful heat. This is why a real biomass contract specifies moisture, ash and net calorific value as delivered, with a sampling protocol and price adjustment clauses, rather than quoting a tonnage.

Ash is where the fuel and the boiler interact

Ash content separates the classes as sharply as moisture does. Clean stemwood pellets sit below one per cent; straw, husks and other agricultural residues commonly run at five to ten per cent, and the composition matters more than the quantity. Cereal straw is rich in potassium and chlorine, which lower the ash melting temperature, so the ash softens and sticks to heat-exchange surfaces instead of falling out as a powder. The result is slagging, fouling and chlorine-driven high-temperature corrosion of superheater tubes. A boiler certified for pellets is not therefore a boiler that can burn straw, and a contract that treats the two as interchangeable tonnage is mispriced.

The collection radius sets the plant size

Biomass has a low energy density per unit volume, so haulage is a large share of delivered cost. The available quantity within a radius grows roughly with the square of that radius, while the average haul distance grows with the radius itself. Delivered cost per unit of energy therefore rises with plant capacity, and it rises without any offsetting technical benefit. That arithmetic, not capital markets, is what keeps solid-biomass trading regional and thin, and it is why a genuinely global benchmark exists only for the one product that has been engineered into uniformity — the industrial wood pellet.

Biomethane escapes by being a molecule

Biomethane is the contrasting case. Once upgraded to grid specification — carbon dioxide and hydrogen sulphide removed, calorific value and Wobbe index inside the network’s band — it is indistinguishable from fossil methane in the same pipe. Physical delivery of a specific molecule is then meaningless, so the traded object is separated from the gas: a guarantee of origin, conventionally one megawatt-hour, issued on injection and cancelled on claim. The instrument’s integrity rests entirely on the registry preventing the same megawatt-hour from being claimed twice, which is a bookkeeping problem, not a chemical one.