Are there any data centers participating DR (Demand Response) programs ? Having backup diesel generators on hand, a data center could get off the grid,(peak shaving)or sell power back to the grid,(Demand Response). Hospitals and other large industries are involved ... just don't know about the data center industry.
And yes, the owners of the generators have to retrofit the engines with DPFs (diesel particulate filters) to meet EPA air quality standards.
One of the European datacenters we use for my hosting company is powered entirely by wind turbines and have been listed by greenpeace as one of the best performers on their renewable energy usage report.