The world largest Cambi THP to be built in Washington DC
The Cambi process will produce biogas and high quality Class A biosolids
fertilizer product, all to be built over a minimum area, saving on both
investment and operational costs compared to conventional digestion.
The biogas will produce green electricity for the plant; reducing its carbon footprint significantly.
"This is the single largest contribution so far to greenhouse gas reduction in
Washington DC. The beauty of it all is that we are investing significantly less
than we would for conventional digestion, and this choice will, in addition,
save us some 20 million dollars in operational costs every year over many years
to come," said Mr. George S. Hawkins, General Manager of DC Water.
The major contract forming part of DC Water’s $400 million (USD) biosolids management
program was signed as a Joint Venture between CDM and PC Construction. This
design-build contract includes thickening, pre-dewatering, four trains of the Cambi
thermal hydrolysis process, and four digesters. In addition, a 14 MW biogas CHP powerplant
contract is soon to be awarded, as well as a post dewatering facility contract.
The plant will reduce DC Water’s carbon footprint by approximately 60,000 tonnes of CO2 per year.
This will be achieved mainly through the generation of green energy, elimination of lime for
stabilization, and reduced truck use for solids disposal and transportation.
The projects have demonstrated the ability to feed digesters at 2-3 times conventional
load and to make a high quality fertilizer cake product.The THP plant for DC Water will have a capacity
for some 400 tonnes of dry solids per day, which will make it the largest THP plant in the world.
The benefits of the Cambi process are:
• Compact digestion plant
• Reduction in volume of cake to half of before situation
• Energy consumption for dewatering
• Cost savings from green electricity production
• Reduction of carbon footprint