He says knowing how to do this may be especially valuable if fossil fuel should become unavailable.Professor Hess says food security is national security.

• 他们还将把树叶，动物废料和来自大学厨房的食物残渣混合起来制作肥料，然后用这些混合物给土壤施肥，而不是购买那些破坏环境的化学肥料。