We all know that green IT can only be built with cloud technology. It is common sense. Fewer physical servers means less energy, means green. Right? Not exactly. But a common assumption, even in the green IT community, is that cloud computing is the only way to achieve green IT. This is, at least on the surface, true, but the reverse is not: Cloud computing is not always green.

The green of IT regularly garners headlines. Some examples from the past year are Facebook’s Open Compute Project Initiative, Google’s Solar initiatives and Ivanpah Solar Electric Generating System(“largest solar energy project in the world”), with more that $168 million invested. Other examples areYahoo’s Chicken Coop Data Center Design: a 155,000-square-foot data center, which can accommodate 50,000 servers, is cooled almost 100 percent by outside air (in contrast to the large power-hungry chillers in most data centers) and uses 40 percent less energy than typical data centers.

One especially interesting project is GreenQloud. In Iceland the data center is powered 100 percent by geothermal and hydropower energy, delivering hosting and storage services.

But at the same time, even as cloud computing has accelerated, so has the number of physical host servers increased. The impact of cloud computing and the explosion of mobile smart phones on data-center infrastructures has created a situation in which green IT objectives (reduced energy costs, cleaner air from reduced hydrocarbon emissions, lower waste products, reduced travel-related environmental impact, etc.) are not automatic and are sometimes even counterproductive. Simply stated, cloud computing alone does not equal energy efficiency.

Let me take a case in point to show how moving to the cloud can sometimes exacerbate environmental problems associated with pollution and waste.

As the numbers of servers which can be run in data centers increases, the cost per server decreases. But this can also can lead to virtual-server bloat with little or even no overall cost reductions. There used to be a joke about how much RAM you need in your server. The answer is always “more.” So too with virtual servers. If the number of virtual servers available is unlimited, how many will people use? Well, more. Virtual-server bloat leads directly to physical-server bloat.

Competition between data-center providers has also led many to search for ways in which to lower operating costs by improving their data center efficiency – for example, by building data centers in colder climates like Scandinavia and Iceland where natural cooling can be utilized. But the search for lower costs can also lead in an environmentally negative direction and increases the attractiveness of building data centers in areas with lower power costs using nuclear energy or brown coal. Technology areas in Oregon and North Carolina are two examples which have enticed several large companies to relocate all or part of their data-center operations despite heavy reliance on coal and nuclear power in those areas. In the case where a data center relocates to either of these two areas, the resulting cloud is not green, but brown.