I have been looking at gasification type boilers for the past year. I have posted the following information before, but in case you missed it I will repeat. I will be burning wood only, so the companies that I have been looking into are: Seton, Garn-WHS, Greenwood - hydronic wood furnace, Alternating Heating Systems - Wood Gun and the New Horizon – EKO.
the Seton and Greenwood are essentially the same unit.
I have also looked into the HS Tarm, but it looks as though the Tarm is somewhat limited to the east coast for installation, support and distribution. they are also one of the most expensive, but they are one of the best.
I have been told that none of these are true gasifiers because a gasifier produces a gas which is piped somewhere else for use.
They are either down draft or just refractory lined burners of various designs.
However, I guess they are, in a way, gasification boilers in that they all burn at very high temps, around 2,000 degrees, in a secondary chamber.
One of the problems is that they cost from 1-1/2 to 2 times that of a standard outdoor furnace.
I think the benefits and return is there to justify the added cost though.
Part of the added costs is that most are pressured boilers.
Some of the benefits of a pressurized system is they typically have a longer operating life span.
They use little or no chemicals.
all of the gasification type boilers burn more efficiently - use about 1/3 less wood than that of a standard out door furnace.
They burn more completely - the secondary chamber reaches temps from 1,500 to 2,000 degrees. At these temps, the gasses and creosote are burned, so there’s less smoke, less ash and very low emissions.
They are physically smaller in size. The exception would be the Garn which stores energy in a water jacket that surrounds the boiler. The Tarm incorporates a stand alone heat storage tank to store the energy.
I think in the near future there will be an EPA maximum emission limit (.250 gm/1,000 BTUs) for out door boilers and furnaces and the only units that I know of that will be able to meet the standards will be the “gasification” type boilers.
I have it narrowed down to either the Garn or the Alternate heating boiler, but that's subject to change.