Automaker General Motors and tech giant Apple have become some of the latest big companies to join RE100, a collaborative initiative made up of some of the planet's biggest businesses, all committed to renewable energy.

Here, CNBC's Sustainable Energy looks at a selection of the high-profile members of RE100, examining their green credentials and their plans for a clean energy future.

Apple became one of RE100's newest members when it announced it was joining the initiative during Climate Week NYC in September 2016.

Apple has made renewables and sustainability a key part of its business.

It says on its website that its facilities in the U.S., China and 21 other countries are powered by 100 percent renewable energy, while as of January 2016, 93 percent of global operations were powered with renewables.

In September 2016, Detroit-based GM announced its plan to source or generate all of its electrical power with 100 percent renewable energy by 2050.

"This pursuit of renewable energy benefits our customers and communities through cleaner air while strengthening our business through lower and more stable energy costs," Mary Barra, chairman and CEO of GM, said in a news release.

GM added in the news release that, currently, it saves $5 million per year by using renewables.

Packaging company Tetra Pak joined RE100 in June 2016 and is committed to increasing its renewable electricity usage from 20 percent to 100 percent by 2030.

The business is already making progress.

Commenting on Tetra Pak's decision, Charles Brand, executive vice president of product management and commercial operations, said on the company's website that emissions in 2015, "were down 15 percent from the 2010 baseline, despite a 16 percent increase in production."

Retailing giant Wal-Mart has big ambitions when it comes to clean energy.

In 2013, the company announced in a news release that it hoped to either produce or procure 7 billion kilowatt hours of renewable energy by 2020, a 600 percent increase compared to 2010 levels.

Together with reinsurance firm, Swiss Re, the IKEA Group is a founding partner of the RE100 initiative.

By 2020, the Swedish business says that it will produce as much renewable energy as it consumes.

It is backing its words up with money: In 2015 the IKEA Group and IKEA Foundation committed 1 billion euros ($1.1 billion) to tackle climate change.

Major food conglomerate Mars has pledged to get rid of all greenhouse gas (GHG) emissions from its operations by 2040.

In 2015 it managed to meet its goal of cutting GHG emissions by 25 percent, according to its website.

In May, Mars signaled its green credentials when it announced its U.K. operations would be completely powered by renewable electricity.

Another recent member of RE100, Bank of America has committed to both carbon neutrality and purchasing 100 percent renewable electricity by 2020.

"Addressing global issues like climate change and the transition to a sustainable and low-carbon future takes collaboration, innovation and investment," Anne Finucane, vice chairman of Bank of America, said in a statement accompanying the bank's announcement last month.