Electricity Has a Grid. Heat Does Not.

One asymmetry decides more about where waste-to-energy plants succeed than most of the engineering does.

Power can be sold anywhere the wires reach. Heat has to be used where it is made, or within a few kilometres of it, through pipes that are expensive to lay and expensive to maintain. That single difference shapes the economics of every thermal plant, and it is routinely treated as an afterthought in projects that have spent years on the reactor.

WHERE THE ENERGY GOES

Convert waste to energy by any thermal route and most of what you release is heat. Only a fraction of that heat can be turned into electricity, because converting heat into power is limited by physics rather than by engineering skill. The remainder has to go somewhere.

In a plant that sells only electricity, it goes up the stack and into the cooling system, as warm air and warm water. Roughly half the energy in the waste - often more - is simply released. The plant has done the hard part, recovering energy from material nobody wanted, and then thrown most of it away.

A plant that sells heat as well captures that remainder. Total energy delivered to a customer can approach double what the electricity-only plant achieves, from the same feedstock, the same reactor and the same operating cost. Nothing about the technology has changed. Only the customer has.

WHO USES HEAT

The heat customer is not exotic. It is anything that currently burns gas to stay warm or to run a process, and would rather not.

• Industry with continuous thermal demand: drying, washing, sterilising, process heating. Food plants, laundries, breweries, paper mills, chemical sites.
• District heating networks, which exist in much of northern and central Europe and are being extended elsewhere specifically to receive low-carbon heat.
• Greenhouses, which need heat on a schedule that matches the seasons rather than the plant's output, and so pair well with thermal storage.
• Large buildings with year-round demand: hospitals, universities, swimming pools, data centres.

The common thread is that the demand is continuous, or close to it. A customer who needs heat for three months a year is a weak partner for a plant that runs for twelve. The ideal is a user whose demand is flat and whose alternative is a gas bill.

THE SITING CONSEQUENCE

If heat is half the value and heat cannot travel, then the location of the plant is determined by the location of the heat customer, not by the location of the waste.

That inverts the usual planning sequence. Most projects start from a waste stream - a municipality with a disposal problem, a site with a landfill closing - and ask where to put a plant. The better question is where the waste can be brought to a heat user, because waste travels far more cheaply than heat does.

A tonne of waste on a lorry is a routine cost. A megawatt of heat in a pipe is a construction project. Between the two, the lorry wins almost every time, which is why the right site is near the factory, the network or the hospital, with the waste delivered to it.

WHY MODEST PLANTS OFTEN WIN HERE

A large plant produces a large, continuous flow of heat, and finding a single customer able to absorb all of it is genuinely hard. The grid can take any amount of electricity. No heat customer can take any amount of heat.

A plant sized to the heat demand that actually exists at a site - a factory's process load, a network's base load - sells all of its heat from the first day. It may be a smaller plant with less impressive headline figures. It is also a plant with a customer for its most valuable output, which the large plant may never find.

This is the quiet reason why many of the most durable waste-to-energy installations are mid-sized and attached to something: an industrial site, a network, a campus. They did not win on technology. They won on having somewhere for the heat to go.

THE HONEST PART

Heat is not free money, and treating it as such has sunk projects.

Heat contracts are harder to write than power contracts. There is no spot market to fall back on. The buyer is a single counterparty, and if that counterparty closes, relocates or changes process, the heat revenue goes with them. A plant financed on heat sales to one factory has a concentration risk that a lender will price.

Heat networks are capital-intensive and slow. Laying pipe through a built-up area is expensive, disruptive and politically sensitive, and the network has to exist before the heat can be sold. Projects that assume a network will be built around them are making an assumption that someone else has to fund.

Demand varies. Industrial customers have shutdowns, maintenance periods and seasonal patterns. The plant's heat output does not stop when the customer's demand does. Without storage, dumping or a secondary customer, the plant is back to venting during those periods - and designing for that costs money.

Heat also has a temperature. A customer who needs high-grade process heat is a different proposition from one who needs warm water for a building. The plant's heat recovery design has to match what the customer can actually use, and the match is not automatic.

None of this undermines the argument. It qualifies it. Heat doubles the value of the plant only where there is a real, durable, contracted customer whose demand profile and temperature requirement the plant can meet.

QUESTIONS WORTH ASKING

• Who buys the heat, and under what contract term?
• What is their current heat cost, and what happens to the plant's economics if that customer disappears?
• What is the demand profile across a year, and how is the mismatch with plant output handled?
• What temperature does the customer need, and does the plant's heat recovery deliver it?
• Is the heat connection built, funded and permitted, or assumed?

A project team that can answer all five has a heat strategy. One that can answer only the first has a hope.

THE QUESTION TO ASK FIRST

Most waste-to-energy projects begin with the waste and end with the plant. The ones that work begin with the heat customer and arrange everything else around them.

Electricity can be sold anywhere. Heat has to be sold next door. Decide who is next door before deciding anything else.

Talk to us at zero-x.co.