Peat

Half-rotted plant matter from waterlogged bogs — the first stage on the road from a swamp to a coal seam.

なぜ重要なのか

Peatlands hold more carbon than all the world's forests, which is why cutting them for fuel and compost is now contested rather than routine.

Where it is in the Earth

Where it is in the Earth

Peat is not a rock in the conventional sense. It is an accumulation of partially decomposed plant material — leaves, stems, roots, mosses — that has built up in waterlogged conditions where the lack of oxygen slows bacterial decay almost to a standstill. Because organic matter is added faster than it breaks down, the unrotted residue compresses under its own weight into a soft, spongy deposit that can, over thousands of years, reach many metres in depth. Left long enough, buried deep enough, and subjected to heat and pressure, peat would eventually become lignite and then harder coals. What we call a peat bog is therefore the earliest recognisable stage of the coal-forming process, caught before burial has gone very far.

The geographical pattern of peat deposits follows the logic of moisture and cool temperatures. Sustained waterlogging is the first requirement, and that tends to occur either where rainfall reliably exceeds evaporation or where flat, poorly drained terrain lets water pond year-round. Both conditions are well met across the high latitudes of the Northern Hemisphere — Finland, Russia, Canada, the Baltic states and Belarus together account for the overwhelming majority of known reserves. Tropical peatlands exist too, particularly in insular Southeast Asia, where deep deposits formed under equatorial rainfall, but those regions feature little in current commercial extraction. The character of the plant community shapes the peat's properties: bogs dominated by Sphagnum mosses tend to be highly fibrous, acidic and low in nutrients, making them valuable for horticulture, while sedge- and reed-dominated fens produce a more decomposed, darker material that has historically been burned as fuel.

The degree of decomposition within a peat profile is described using the von Post scale, which runs from H1 (entirely undecomposed, water squeezed from the peat is clear) to H10 (completely amorphous, no plant structure visible). Near the surface of an undisturbed bog, von Post values are typically low; deeper layers, under greater pressure and having had longer to decompose anaerobically, read higher on the scale. Harvesters and processors pay close attention to this gradient because horticulture buyers generally want lightly decomposed, fibrous material, while energy applications historically preferred the more humified, denser lower layers.

Getting it out

Getting it out

Peat extraction is essentially a surface operation. The deposit lies at or very close to ground level, so there is no underground mining, no shaft sinking and no blasting of hard rock. The practical challenge is almost the opposite: the material is waterlogged and structurally weak, and the working surface is too soft to support heavy equipment without preparation. Before any harvest begins, an area is drained by cutting a network of drainage ditches — a process that can take several seasons before the upper peat layer is dry enough to work. Vegetation is then stripped from the surface and the exposed peat is allowed to dry further under ambient conditions.

Two main harvesting methods are in use. In milled peat production, a rotating drum fitted with cutting teeth shaves a thin layer — typically a few centimetres — from the surface. This milled material is spread to dry in the open air, then harrowed to speed drying, then collected by vacuum harvesters and stacked into storage ridges. The cycle repeats until the growing season ends or rainfall interrupts. Because each pass removes only a small thickness, a productive season may involve many individual cuts across the same field. In sod peat production, extruded sausage-shaped blocks are cut from the surface and left to dry in rows before collection; this method is older and less mechanised, now mostly confined to small-scale or traditional fuel use.

Waste in the conventional sense is minimal — nearly everything removed from the field is saleable in some grade. What does vary greatly is the yield of usable product per hectare per season, which depends heavily on weather, the depth and von Post rating of the deposit, and how far drainage has progressed. The environmental footprint, however, is large relative to the volume extracted. Draining a bog releases carbon dioxide from the now-aerobic peat below the water table, and the surface disturbance destroys the habitat that accumulated the deposit over millennia. This asymmetry — fast extraction, very slow natural regeneration — is the central reason that peat harvesting is subject to increasing regulatory scrutiny in many producing countries.

What pulls on it

What pulls on it

Peat serves two quite distinct markets that have followed opposite trajectories over recent decades. The horticultural market — growing media for professional nurseries, mushroom cultivation substrates, and retail garden composts — has remained the more durable of the two. Commercial horticulture values Sphagnum peat for properties that are genuinely difficult to replicate cheaply at scale: consistent particle structure, stable chemistry, low nutrient content that gives growers precise control over feeding, and reliable water retention combined with good drainage. Canada supplies a large share of this market internationally, with the United States being by far the dominant destination for Canadian production, as the import reliance figure in the statistics table indicates.

Energy use of peat tells a different story. Several northern European countries, most notably Finland and Ireland, built electricity generating capacity and district heating systems around domestic peat, treating it as a locally available solid fuel at a time when energy security arguments favoured indigenous resources over imported coal or gas. That logic has weakened considerably as climate policy has tightened. Peat releases carbon dioxide when burned, and its harvest also releases stored carbon from the drained bog below — giving it a carbon footprint that compares unfavourably even with coal on some accounting methods. Policy-driven reductions in peat burning for electricity and heat are already visible in production statistics from Finland and several other European producers, and this contraction is expected to continue as emissions targets take effect.

For demand to shift sharply in the horticultural segment, a substitute would need to match peat's physical and chemical consistency at comparable cost and at the volumes required by industrial-scale nurseries. For energy use, the direction of change is already determined by policy rather than price: the question is the pace of wind-down rather than whether it will occur. The carbon-sequestration value of intact peatlands is increasingly being recognised in environmental accounting, which adds a further policy dimension to the economic case for extraction.

Turning ore into product レベル 3

Turning ore into product

Peat undergoes relatively little processing compared with most mined commodities. The transformation from field to product is dominated by drying, screening and grading rather than by chemical or thermal treatment. Air-drying in the field reduces moisture content from the very high levels found in freshly cut peat to something closer to the air-dried basis on which commercial weights are reported. The moisture remaining at sale is still significant and is a source of discrepancy between production figures measured at different stages in the chain; the data shown in the production table use an air-dried basis, which is the standard unit for most trade statistics.

After collection and primary drying, peat is screened to separate particle sizes. Horticultural grades are differentiated principally by fibre length and degree of decomposition: coarse, fibrous Sphagnum peat commands a premium for professional growing media because its open structure retains both air and water, while finer, more decomposed fractions are blended into lower-cost retail composts. Some producers carry out further processing — wetting agents are added to counteract the hydrophobic tendency of very dry peat, and pH may be adjusted for specific crop applications — but these are blending and conditioning steps rather than metallurgical-scale refining. For fuel peat, the main processing variable is final moisture content, since calorific value (the energy released per kilogram on combustion) is directly reduced by residual water. Some Finnish and Irish producers have operated briquetting plants that compress dried milled peat into a denser, more handleable form, reducing transport cost per unit of energy.

Losses in the peat processing chain are largely invisible in production statistics because they take the form of material that is too wet, too fine, or too decomposed to meet specification and is left on the bog or returned to the field. No beneficiation step in the mineral-processing sense — no flotation, leaching or smelting — is involved. The main cost drivers are fuel for drying machinery and haulage, weather-related downtime, and the capital and operating cost of the drainage infrastructure that makes harvesting possible in the first place.

Substitution and recycling レベル 3

Substitution and recycling

Peat is not recycled in any meaningful sense — once extracted and used, it is gone. The practical question of substitution is therefore entirely about what can replace it in its end uses. For energy applications, the substitutes are other solid fuels, biomass, or the switch to gas or electricity, and in that context peat has no particular advantage over alternatives. The shift away from peat in power generation has proceeded largely on the basis of carbon accounting rather than any physical difficulty of substitution.

In horticulture, substitution is harder to achieve at scale. The principal candidates are composted bark, wood fibre, coir (coconut husk fibre), composted green waste, and digestate from anaerobic digestion. Each has limitations. Coir is structurally similar to Sphagnum peat but is a product of the coconut processing industry concentrated in tropical countries, bringing its own supply geography and transport footprint. Wood fibre can replicate some of peat's air-filled porosity but tends to be biologically less stable, consuming nitrogen as it continues to decompose in the growing medium. Composted materials are variable in quality and harder to standardise to the specifications that commercial growers require. None of these alternatives is intrinsically inferior for all applications, but the transition requires reformulation of growing recipes, adjustment of irrigation and nutrition regimes, and acceptance of some yield variability during the learning period — costs that slow adoption even where growers are willing in principle.

Several European countries have introduced timetables to restrict or end horticultural peat use, particularly in the retail amateur gardening sector where alternatives are generally considered adequate. Professional and export-facing horticulture has been given longer transition periods in most jurisdictions, reflecting the greater technical difficulty of substitution at scale. The pace at which alternatives can genuinely replace peat at the volumes the industry requires remains the central uncertainty in the horticultural supply chain.

Where the chain is fragile レベル 4

Where the chain is fragile

The supply picture for peat is unusual among raw materials in that physical scarcity is not the primary risk. The reserve figures in the table show that known deposits greatly exceed any plausible production horizon at current extraction rates. The fragility lies instead in the regulatory and social licence dimension. Peat harvesting requires permits that are increasingly difficult to obtain in countries with active climate and biodiversity policy. Finland holds by far the largest share of stated reserves, yet domestic policy pressure on peat extraction has been building for years, and the gap between theoretical reserves and practically accessible deposits is widening rather than narrowing. Sweden's and Poland's reserves are shown as withheld by the source, which in itself reflects the sensitivity of reporting in a commodity whose extraction is contested.

The production geography creates a secondary concentration risk in the horticultural trade. Canada is reported as the dominant source of U.S. imports over the 2021–2024 period, and the U.S. net import reliance figure for 2025 is estimated at 80 percent. This is a tighter bilateral dependency than exists for many other commodity trade flows, and it rests on a production base — Canadian Sphagnum bogs, primarily in Quebec and the Maritime provinces — that is itself subject to provincial land-use regulation. Any significant restriction on new extraction licences in Canada would have a disproportionate effect on North American horticultural supply.

Reporting conventions introduce further uncertainty into the published statistics. Figures are given on an air-dried weight basis, but moisture content at the point of measurement varies between producers and even between seasons, meaning that apparent changes in tonnage between years can partly reflect differences in drying conditions rather than real changes in production volume. The energy content of fuel peat and the physical properties of horticultural peat are not captured in weight-based statistics at all, so the production table gives only a partial picture of what is actually being traded. Researchers working with these data should treat year-on-year comparisons with caution and look for corroborating evidence from trade flow data and end-market consumption surveys before drawing conclusions about trends.