The alternative

This is in respect to the system mentioned in the previous post.

The alternative would be an internal combustion engine, as opposed to the Stirling engine.  The problem with the internal combustion system, aside from the other problems, which are well known, is that cannot handle syngas without some major modifications.

To deal with that problem, you can convert the syngas into methanol, and then use that.  It is one more level of complexity that I would just as soon avoid.

However, an internal combustion engine would not be hard to find and it would be cheap.  On the other hand, making methanol may not be all that hard, however it is yet another skill that would have to be learned.