A report from investment firm Village Capital has suggested cleantech investors should focus more on the transportation sector in the struggle to cut carbon emissions.

The report, called Moving Electrons and co-sponsored by the Autodesk Foundation, points to transport as the single biggest source of carbon dioxide emissions.

It listed five subsectors that could prove particularly attractive to investors: aviation and aerospace, electric vehicles, the sharing economy, mass transit, and trucking and logistics.

In aviation, said the report, growing air traffic, shrinking fares and increasing emissions regulations are putting pressure on fuel costs. This means “there are rich opportunities for startups that operate, manufacture or enhance low-emissions aircraft.”

The electric-vehicle market, meanwhile, presents strong opportunities in lithium-ion battery manufacturing and charging technology. Battery investment topped $641.5 million across 55 deals in 2017, according to the report.

Alongside electric vehicles, Village Capital called out ride sharing as part of a cleantech investment strategy. “The $36 billion global ride-sharing industry is poised for rapid, sustained growth,” it said.

Of the other two transportation subsectors Village Capital said investors should focus on, mass transit pulled in $741.2 million in funding in 2017. It includes hyperloop-related investment opportunities such as Elon Musk’s tunneling venture, The Boring Company.

Finally, the trucking and logistics subsector, which Musk is also targeting with the Tesla Semi, is adopting energy-efficiency software and hardware. It attracted more than $2 billion in funding during 2017.

Along with these five subsectors, Village Capital pointed to other important investment opportunities in bioenergy, compressed natural gas, plastics and fibers, and oil and gas refining and distribution.

“We brought together a rich advisory board to help us identify and iterate on some of the trends we’ve been seeing,” said Allie Burns, Village Capital’s managing director.

The report was based on Village Capital's sourcing process, which included feedback from Generate Capital President and GTM regular Jigar Shah, Hewlett Foundation environment program Officer Marilyn Waite, CleanChoice Energy co-founder Richard Graves and BP innovation expert Miriam Eaves.

Burns said the firm wants to boost broader investor interest in the cleantech sector, after a long period of sluggish activity. “We’re seeing things turn in a more positive direction, but after 2008 there were a lot of investors who didn’t really have specific knowledge of the landscape for investing in clean energy, and a lot of money went into companies that ultimately failed,” she said.

That scared investors away, she said. Cleantech venture investment in the U.S. fell from $7.5 billion in 2011 to $5 billion in 2016. This represented a drop from 17 percent to 7 percent of total venture capital funding in the country, she said.

Investors are now beginning to realize that cleantech funding has different requirements compared to other sectors, such as the need for larger capital inputs and longer investment horizons, said Burns. Even so, there are lingering problems in matching startups to investors, which Village Capital is working to solve with an investment-readiness framework that can be used by all parties.

And knowing what subsectors might offer the best chances of investment success could also help stimulate venture capital interest, Burns said.

“One of the reasons we focused on five sectors in particular is because we think they have the highest potential for growth at the current time,” she said.

Village Capital’s approach is the latest in a long line of attempts to "fix" cleantech investing.

Last month, for example, Congruent Ventures closed a $92 million fund to invest in early-stage startups in the sustainability space, with founders Abe Yokell and Joshua Posamentier determined to prove that the cleantech sector is still worth betting on.

Meanwhile, many startups are now being fostered via incubator programs.