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Comment by sschueller | Hacker News Reader

Pellets in Switzerland are all from local Forrest that are specifically used for this. The manufacturing of pellets requires no additives and if 4 or more homes are sharing a burner (recommended) the burner has to meet very strict emissions and needs to be inspected regularly. Because the resources are local and the burning only produces CO2 which is planted again, it is considered quite sustainable.

If course a geo thermal heat pump and solar would be better but not every one has 100k extra to get that installed.

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I honestly doubt that 100% of Swiss pellets came from Swiss... It would be FAR more expensive and if in Swiss pellets are common like in France or Italy... Swiss pellets production will erase forests in a decade.

Beside that pellets in general is not sustainable due to the usage scale: wood is renewable BUT at a certain rate. If we all heat with pellets the usage rate is simply too high. Solar + heat pumps is nice IF you do not need much heat AND you have enough sunlight AND a veeery big hot water storage: I'm actually evaluating this for my home, witch is new "Minergie/A class" kind, with a small p.v. plant, with potentially enough room for insulated storage in sufficient quantity and well... I need at least 3000l of water, 10kWp solar to pass a single SUNNY winter day 100% on local energy for heating (witch means not counting water circulatory pumps etc). It's potentially feasible on scale, but IF and only IF we re-build all homes, annihilating condominiums, limiting the change to Europe south/center. Oh and heat pumps compressors does not last more than 10 years in general... It's not just a matter of costs, it's also a matter of scale.

How quickly is each consumed tree replaced, how quickly is the CO2 from the entire supply chain recaptured, and how quickly does the other pollutants degrade?

If it takes years to recreate the resources or recapture the CO2 from what is burnt in the course of days, then it is pretty grotesque to call it sustainable, but maybe the numbers show otherwise?

If everybody shares burners for highly processed pelletized wood that lives up to power-plant like smoke processing requirements (how many would you say do? 90%? 20%?), then indeed you might be able to just being as bad as coal... Which is horrible.

Air-to-water heatpumps are also an option, no need to compare to the heating solution with the highest installation cost.

Depends on the surface area of the forest. A single tree takes tens of years to grow but a certain area of forest contains enough growing trees that by the time you cut down the last the one you planted first has grown to full.

Do note that a tree that dies in forest also produces CO2. Exactly the amount it does if it’s burned (unless it’s a peat bog or whatnot). So not burning it doesn’t really change things.

> Do note that a tree that dies in forest also produces CO2. Exactly the amount it does if it’s burned (unless it’s a peat bog or whatnot). So not burning it doesn’t really change things.

Growing trees require more than just CO2, and I imagine there are limits to how much this process can be accelerated without environmental impact. Depending on the tree sort and location they may naturally live for long enough to be considered immortal for all practical purposes, so felling the tree after only 10 years presents a very significant increase in tree turnover, and as the tree is taken away it does not fertilize the soil again, so there's a significant increase in soil nutrient and water requirements in the area.

Plus, the felling operation, timber processing and pellet production require large amounts of energy. There is a significant environmental load even if the pellets are never burnt to release the stored CO2.

So yes, it changes things a whole lot.

Here in the US I don't think I've ever heard of a shared burner between multiple homes. It seems like an interesting idea. How common are these? How does it typically work? Does one home owner sell heat to the neighbors, or is it jointly owned? Or is there no "typical", and it's always a custom arrangement?

It’s just a heat exchanger glycol loop that uses burning wood to generate the heat, very similar to a gas-fired boiler. With a large enough burner you can have multiple heat exchangers or multiple glycol loops with a large heat exchanger for multiple buildings, similar to how commercial buildings use a single boiler or chiller to heat/cool large buildings or multiple buildings that need multiple heating or cooling glycol loops.

Most of the houses that burn wood for heat in the US are in sparsely populated rural areas where sharing a burner wouldn’t make sense due to the loop length and pumps needed to circulate the glycol. Densely populated areas in the US that need lots of winter heating generally have natural gas distribution networks.

I don't know about typical, but I know a couple of people (here in Switzerland) using pellets and they jointly (that is, together with their neighbours) own the burner. They made the investment together and pay for all expenses together. I also heared that it makes most sense for a densly populated area like an old town (talking about european old towns) or big buildings like a school. Doesn't make too much sense if every one-family home has their own.

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