At the Nestlé coffee plant in Mainz, Germany, spent coffee solids (left over from the production process) are burned to create energy to power a further stage of production, helping to reduce energy consumption and costs, and CO2 emissions. In September 2007, the Mainz factory received its first batch of 4C-verified coffee, grown in Vietnam. 4C is a voluntary code adopted by coffee producers, traders and others involved in coffee growing, processing and trading. It commits members to good farming and management methods to improve efficiency, profitability, transparency and sustainability. As of December 2007, 6% of the world’s coffee supply was 4C-verified. Nestlé supports 4C through its value chain, for example, by procuring 4C coffee and supporting growers and others working within the scheme.