One of the smart people I get to have regular conversations with is Pat Kennedy, Founder and CEO of OSIsoft.  Pat is the one who got me thinking about green data centers when he asked a simple question three years ago, "how do you measure the power consumption of an application in a data center?"  This got me started down a whole path of monitoring and modeling.

One of the latest topics Pat and I have discussed is MicroGrids.  Google thinks about this too.  See this Google video, I can see some of the Google data center team in the audience.

HP is making news today with their paper on a microgrid for data centers powered by cow manure.

ABSTRACT
In this paper, we design a supply-side infrastructure for data centers that runs primarily on energy from digested farm waste. Although the information technology and livestock industries may seem completely disjoint, they have complementary characteristics that we exploit for mutual benefit. In particular, the farm waste fuels a combined heat and power system. The data center consumes the power, and its waste heat feeds back into the combined system. We propose a resource management system to manage the resource flows and effluents, and evaluate the direct and indirect economic benefits. As an example, we explain how a hypothetical farm of 10,000 dairy cows could fulfill the power requirements of a 1MW data center.

Pat Kennedy long ago was making the point that data centers could be a lot efficient if sites were chosen to be next to power generation, biomass, and/or other large consumer of power.  But, this idea is controversial in that a standard practice for data center risk reduction to place data centers far away from hazardous materials.  I think a large methane store would typically get classified as a risk to a data center.  So, if you are totally risk averse and don't pay for the power bill, why not skip over the site with methane.  Most would.

Plus there are risks that HP doesn't mention in their brief statement on financial and associated risks.

Financial cost and associated risks are perhaps the most
important consideration. Existing farms that have invested in
supply-side infrastructure often do so only if a power-purchase
agreement can be signed. Otherwise, the return could be too
speculative to justify the capital investment. A data center has substantial, continuous, and long-term power needs. Thus the data center owner could sign the power purchase agreement and provide the assured return desired by the farmer.

You are now dependent on a Farm.  What is the #1 risk to your manure production?  Water!!!  When there is a drought there is an impact to agriculture production and cattle need a lot of water.  This article says it takes 2,000 gallons of water to make a gallon of milk.

It can take up to 2,000 gallons of water to produce one gallon of milk. The cow needs water to perform basic biological functions from day to day, and only a fraction of the water the cow consumes is actually converted into milk. The fact that it takes so much water to produce cow's milk means that anytime you or any consumer chooses to drink milk, the burden you place on the natural environment is a thousand times greater than if you were to consume water itself. Drinking one gallon of milk is like pouring 1,999 gallons of fresh water down the drain.

Actually putting a data center in operation using a Farm has these risks like water and methane gas.  There are a bunch of other issues that can be addressed like water. 

Mike Manos and I regularly discuss that water is the next scarce resource for data centers.  Be careful not thinking about the secondary and tertiary affects of a change in the water supply.

I congratulate the guys at HP for creating more awareness that a microgrid data center strategy has merit.