Reductions. The voluntary Chicago Climate Exchange also includes a carbon offset scheme that allows offset project developers to sell emissions reductions to CCX members who have voluntarily agreed to meet emissions reduction targets. The Western Climate Initiative, a regional greenhouse gas reduction initiative by states and provinces along the western rim of North America, includes an offset scheme. Likewise, the Regional Greenhouse Gas Initiative, a similar program in the northeastern U.S., includes an offset program. A credit mechanism that uses offsets may be incorporated in proposed schemes such as the Australian Carbon Exchange. Carbon retirement Carbon retirement involves retiring allowances from emission trading schemes as a method for offsetting carbon emissions. Voluntary purchasers can offset their carbon emissions by purchasing carbon allowances from legally mandated cap-and-trade programs such as the Regional Greenhouse Gas Initiative or the European Emissions Trading Scheme. By purchasing the allowances that power plants, oil refineries, and industrial facilities need to hold to comply with a cap, voluntary purchases tighten the cap and force additional emissions reductions. Small-scale schemes Voluntary purchases can also be made through small-scale and sometimes uncertified schemes such as those offered at South African-based Promoting Access to Carbon Equity Centre (PACE), which nevertheless offer clear services such as poverty alleviation in the form of renewable energy development. These projects have the potential to develop projects that are either too small or too complicated to benefit from legally mandated cap-and-trade programs. Other A UK offset provider set up a carbon offsetting scheme that set up a secondary market for treadle pumps in developing countries. These pumps are used by farmers, using human power, in place of diesel pumps. However, given that treadle pumps are best suited to pumping shallow water, while diesel pumps are usually used to pump water from deep boreholes, it is not clear that the treadle pumps are actually achieving real emissions reductions. Other companies have explored and rejected treadle pumps as a viable carbon offsetting approach due to these concerns. Quality assurance schemes Accounting for and verifying reductions Owing to their indirect nature, many types of offset are difficult to verify. Some providers obtain independent certification that their offsets are accurately measured to distance themselves from potentially fraudulent competitors. The credibility of the various certification providers is often questioned. Certified offsets may be purchased from commercial or non-profit organizations for US$2.75–99.00 per tonne of CO2, due to fluctuations of market