*Combine with solar thermal heat source to make a ''solar pyrolysis unit'' for charcoal production
==== Terra preta ====
[[Terra preta]] is a type of very dark, fertile anthropogenic soil found in the Amazon Basin. It is basically a mixture of charcoal, bone, and manure. It is very stable and remains in the soil for thousands of years.
=== Biochar Reactors ===
Several small-scale units have been devised for baking charcoal, many with simple common materials. Charcoal making ([[pyrolisis]]) dates back thousands of years in human history, traditionally practiced via earthen pits and mounds. Today, steel drums of different sizes are most commonly utilized due to portability, airflow control options, heat resistance, and availability. See articles below for some examples, and a page on [[Simple Biochar Kilns]].
=== Suitable feedstocks ===
A variety of feedstocks can be used. Since these often constitute agricultural residues in [[rural communities]], a form of waste is turned into an asset. Possible feedstocks include:
*'''agricultural leftovers:''' straw, rice hulls, corn stalks, chicken/cattle poop
*'''Fast-growing biomass:''' bamboo, switchgrass, miscanthus,
*'''Other:''' leaf litter, grasses, macroalgae, bones (high P content),
== Criticism ==