As I did, a serious of papers were published in using waste contents in manufacturing bricks such as(paper,plastic,wood and other waste contents).You can reduce waste and improve resulting brick properties by using waste contents, see my published works.

Waste management is in need of separation processes that facilitate the subsequent separation of the materials or the conversion of the separated materials into more valuable products. For example, the removal of organic matter from municipal solid waste would facilitate the recovery of plastics, paper and other materials.

Composting of Municipal Solid Waste is an important application area in Mechanical Engineering.

Also combustion/incineration of hospital waste also lies in Mechanical Engineering domain.

Reduction of automobile emission is an important aspect of Mechanical Engineering.

There are unlimited applications and other researchers can comment well.

Another area you can look into is power generation and biogas production using waste produced by hotel and hospitality industries.

Municipal Solid Waste incinerators provided with Heat Recovery for Power generation or Cogeneration purposes.

Construction of solid waste digester for generation of biogas, bioethanol and char may be suitable for mechanical engineering.

Another future area would be physical beneficiation of automobile, electrical and electronic waste!

Using the main parts of Municipal Solid Waste (such as plastic and Paper) in producing different kinds of composites can be good examples in this respect.

While the engineering may work for dealing with waste the economics of biogas and composting escape me. For other than rural or small volume applications.... the economics of biogas and composting do not meet industrial investment requirements. Can anyone provide me with information that shows the payback period is between 24 and 36 months? As this is the rate of return level I am being asked to deliver from industrial waste generators.