On balance, the former nomads should be subsistence farming to support themselves, not to export food.
The production of biofuel in a developed country is excellent, but in a developing country, the profit motive of the farmers says "Sell to the biofuel guys for more money." This is simple profit motive.
Anyway, who cares about those guys? They're not us.
Meanwhile Stateside, we can simply use our awesome First World powers to mass-produce biofuel, much to the consternation of the Saudi oil barons.
The widespread deforestation that results from an expansion of operations is deplorable, if only in opportunity costs for later exploitation, but it is cheaper to do it, and cheap means we pay less here, so we keep our America-gold at home.
I applaud the efforts of small communities to achieve self-sufficiency by using their own crops as biofuels, but the mass production of biofuel crops must stop. The environmental benefits of biofuels have been exaggerated - biofuels themselves produce greenhouse gases during combustion, and some studies have claimed that they do not emit significantly less than traditional fuels - and the environmental drawbacks have been largely ignored. Sure, crops absorb carbon dioxide, but that does not mean biofuels are carbon neutral because of opportunity costs - forests with far larger biomass are felled to make way for fields for biofuel crops, particularly in tropical rainforest regions with diverse habitats. Biodiesel has been nicknamed deforestation diesel for this reason. Moreover, biofuel crop production has double food prices in places of Africa, seriously aggravating famine. Some subsistence farmers and nomadic herders (who should not be practising sedentary agriculture in the first place) have been worse off since they switched to biofuel production.