OAK BROOK, IL — A McDonald's potato supplier in Austria turns its potato waste into power for the public grid. Another supplier in the U.K. is providing electricity in a different way; it uses wind turbines to run a French fry factory and sells surplus energy to the grid.

Those are just two of the projects McDonald's has added to its list of best practices, divided into two categories: Best of Green, which are practices created by the company and its stores, and Sustainable Supply, which are from McDonald's suppliers.

The best practices lists are available as downloadable PDFs or can be viewed online, where you can search by keyword, look at practices divided by category or see what is being done in certain parts of the world.

The Austrian supplier, Frisch & Frost, processes all of the liquid and solid waste from potatoes in its own biogas plant. The solid material is converted into gas that is used to provide electricity to the public grid and also create heat that is used to preheat the dryer for the French fry production process. The residue from the conversion of potatoes to gas is provided to potato farmers for use as fertilizer.

Frisch & Frost's organic gas facility creates about 6 gigawatt hours of energy a year, enough to power about 2,000 homes, according to McDonald's. The heat recovery process that powers the dryer produces 4.2 gigawatt hours a year. Altogether, the energy created from potato waste covers about 40 percent of the facility's electricity and energy needs.

McCain Foods in the U.K., on the other hand, spent £10 million to construct three wind turbines that provide 60 percent of the electricity required by its French fry factory in Whittlesey. When the plant isn't operating, any extra electricity is sold to the grid.

The Best of Green and Sustainable Supply lists cover a variety of other practices such as packaging, waste, water, recycling, restaurants and sustainable food.

More than half of McDonald's locations in the U.S., for example, collect and recycle their waste cooking oil.

McDonald's Germany uses McEnvi, a proprietary software, to manage the waste from 50 restaurants, allowing them to plan and track the quantities and costs of waste.

And in the U.K., 11 restaurants in Sheffield send waste to be turned into energy and test technologies that could have positive environmental benefits.

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