Let’s assume we needed to be totally portable. And we only a have hook up of 120 V at 15 A. So my monster air compressor, it is now out of the running... I don’t want to use propane! (Maybe just a small torch if needed.) I only want to use diesel & recycled car engine oil...but mainly engine oil. Remember this is portable. (No 30 foot rigging for elevation to pressurize The fuel source. In 20 to 30°C outside temperatures.) Enough combustion to melt cast-iron. Remember I’m new to this game. But I’m sure if we all put our minds together... maybe I’ll/we’ll come up with something! The reason I am asking this is, I might be building this summer a small foundry shed in my backyard with primary heating source being used motor oil.