Add biomass fuel strategy: 60 rai coppice idea and northern fuel market

Own land yields ~80-135 t/yr vs ~350-400 t/yr mature demand; forestry
classification check gates everything; staged electric-first path with
coppice planted now for the expansion-phase biomass boiler

docs/biomass.md

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+# Biomass Fuel Strategy
+
+If the steam boiler goes the biomass route (see the options in
+[sustainability](sustainability.md) and the Getabec candidate in the
+[utilities CSV](finance/utilities-investment.csv)), the fuel comes from two
+sources: the team's own 60 rai of currently unused land, and northern
+Thailand's agricultural waste market. Figures below are planning estimates,
+plus or minus a wide margin, to be refined against the actual boiler choice
+and duty cycle.
+
+## Demand: what the boiler would burn
+
+The 400 kg/h boiler is roughly 300 kW thermal at full fire. With the heat
+recovery architecture trimming the load and realistic duty cycles:
+
+- Mature plant (semi-auto plus automated lines, two shifts, ~300 days/yr):
+  roughly **350 to 400 tonnes of air-dry wood per year** (at ~80% boiler
+  efficiency and ~4 kWh/kg air-dry wood)
+- Early operations (one press line, single shift): roughly a quarter of
+  that, **~90 to 100 t/yr**
+
+## The 60 rai: own-grown fuelwood
+
+60 rai is 9.6 hectares. Managed as short-rotation coppice (planted once,
+harvested on a 2 to 4 year cycle, regrowing from the stump), fast species
+proven in Thailand (eucalyptus, acacia, leucaena, bamboo) yield roughly 8 to
+14 air-dry tonnes per hectare per year. So the land can sustainably supply
+about **80 to 135 t/yr**:
+
+- Enough to cover **most or all of early operations**
+- About **a quarter to a third of mature two-shift demand**
+
+That makes the land a meaningful supplement and a strong brand story
+("records pressed with steam from our own trees"), not a complete fuel
+supply.
+
+### The classification check comes first
+
+The land is currently classified as forestry, and in Thailand that carries
+legal weight. Before a single tree enters the fuel plan:
+
+- Verify the parcel's actual status: clean Chanote title vs Sor Por Kor vs
+  National Forest Reserve. Planting, harvesting, and transporting trees,
+  even self-planted ones, can be restricted depending on classification,
+  and some species are restricted regardless.
+- If eligible, register the plantation under the forest plantation
+  framework, which legalizes grow-and-harvest cycles and the transport
+  paperwork.
+- If the parcel carries actual standing forest, it should not be harvested
+  for fuel: that would undercut the sustainability commitments the plant is
+  built on. Coppice belongs on the degraded or empty portions.
+
+## Filling the gap: the northern biomass market
+
+The region fills the remainder easily and cheaply:
+
+- **Longan orchard prunings**: Lamphun is Thailand's longan heartland and
+  prunings are an established traded fuel
+- **Sawmill and wood-processing residues**
+- **Corn cobs and rice husk**: abundant regional crop wastes; a
+  Getabec-class solid-fuel boiler is designed for exactly this fuel mix
+- Buying from local farmers also strengthens the local-sourcing story that
+  already runs through packaging and PVC
+
+## Logistics on site
+
+To reflect in the facility planning: a fuel storage shed (biomass
+must be kept dry; monsoon-season storage sizing matters more than dry
+season), chipping for coppice wood, ash handling, and the emissions stack
+that comes with solid fuel. These are the capex/opex adders that the
+biomass premium in the utilities CSV (roughly 4M to 7M THB for the boiler
+package vs 2.5M to 4M electric/gas) partially reflects; fuel handling and
+storage are additional.
+
+## Decision framing
+
+- Biomass makes the steam genuinely renewable and pairs with cheap northern
+  fuel, at the cost of higher capex, fuel logistics, ash, and an emissions
+  point
+- The 60 rai tilts the economics and the story further toward biomass, but
+  only after the land-title check clears
+- The electric boiler remains the alternative: cleanest permitting, no fuel
+  logistics, but effectively grid-powered steam at a ~300 kW draw
+- A staged path is possible: start electric (fast, clean permitting), plant
+  the coppice now (first harvest in 2 to 4 years), and add the biomass
+  boiler at the automated-line expansion when demand and the fuel supply
+  have both matured