There is an ongoing work to limit Arlanda's negative impact on the environment. In an effort to save electricity, buildings at Arlanda use district heating with biofuels and district cooling with water from a nearby lake. The take off charges for aircraft are partly based on the environmental performance of the aircraft and Arlanda is experimenting with Continuous Descent Approaches and landings, often referred to as "green landings". Jet fuel is since around 2006 delivered by boat to Gävle and via train to Brista close to Märsta and from there through pipeline. Previously fuel was delivered by ship to Värtahamnen in Stockholm and then by trucks through Stockholm city to Arlanda. The airport also takes measures to promote the use of bio fuel in taxis operating to and from the airport.