The UK government's review of the Renewables Obligation (RO) support mechanism looks like being a lengthy business as energy minister Mike O'Brien launches the preliminary consultation. This follows last year's consultation on, and publication of, the terms of reference for the review. The preliminary consultation document sets out a range of policy options for improving the effectiveness of the RO, but seeks to avoid any fundamental changes that could weaken confidence in the market framework. The review will look at the RO's effectiveness so far, its working arrangements, the levels of the RO beyond 2015/16, future cost competitiveness of renewable technologies, and energy from mixed wastes. Accompanying the review document is supporting research by independent consultants Oxera and Enviros. This research shows that none of the renewable technologies currently supported would be commercially viable outside the RO. Some technologies, however, do not need the full support of the obligation to be viable, it finds. The government is considering reducing support for future projects for some technologies. But because of the varying economics of different wind sites, it as yet finds no clear cut case for decreasing support for onshore wind. A statutory consultation document with the government's final proposals will be published this summer.