Better understanding the pyrolysis reaction I'm no chemist, but much of my work revolves around biochar.  I've always understood it with the following rough approximation:

$$
\ce{CH2O (dry plant matter) + heat -&gt; black carbon + H2 + CO + CH4 + hydrocarbons}
$$

I've got two questions:


Is the above a decent approximation?  In what ways is it misleading (as all approximations always are)?
A colleague recently told me that methane is only formed in this reaction when there is water vapor present -- he said that it mixes with CO at high temperature to form the methane.  Is this true?  Will one not get any methane from oven-dried biomass that is exposed to heat in the absence of oxygen?
The presumption here is that the biomass is purely sugars: glucose- and xylose-based starches and cellulose.  The essential components of lignin, which make up about 20% of the biomass, is phenols and propane. You may need to rebalance based on those additional components.