Growing rape seed mustard could be attempted in Europe on set aside lands but look at the situation in tropical countries.

Burning cow dung cake takes away organic matter from the recycling and leads to soils poor in humus and gradually soil erosion leads to reducing agricultural production

Presnt is taking away whatever is left for firewood  from the forests and no mans land or from fields 
Burning whatever biomass is available is next option.
People store biomass in front of their houses .

In addition to plnats being removed for the burning without replanting them and thus promoting desertification huge cattle pressure on vegetation is playing havoc in fragile ecosystem.
There are three times more cattles to the inhabitants and more so in drier climates of tropical regions of the world. Sheeps, goats, cows and camels brows at different levels of vegetation and are   is common animal for in the tropical regions of the world additing to removal of vegetation at the level of herbs, shrubs and trees. The fragile ecosystem is then easily destroyed by flood waters and erosion of soil from river banks distort the banks of the rivers and you have seen the floods engulfing crops, lands and human inhabitation.

Its more important to find local solutions for global problems.
Sustainable development of agriculture, regeneration of biomass, restoration of forests, preventing soil erosion and finding new resources of biomass which can grow in adverse climatic conditions and produce enough biomass on renewable basis is need of the hour. One or two crops are good to follow but a comprehensive review of the situation is essential and green house gas emission is serious problem but deforestation is still bigger . The recent floods , scorching heat, burning regions are all man made activities. Try to correct them before nature takes its toll again in thousands of human lives or who knows what is next to come. Climate change is taking place or not I dont know but climate destruction is taking place. Plant trees to save our  planet the only place for humans to live tilll we find some ways to live on moon or mars mother earth is the only chance of survival of human race.