In order to drive sustainability throughout an organization, it really helps to involve and inspire employees. Ideally, they should feel that the company they work for has a greater societal purpose than just squeezing out higher and higher margins to pass along to shareholders. The company should foster trust, and help its workers to feel aligned with its broader purpose. If employees are encouraged to contribute in small ways in their daily lives and can see the effects of their actions, they will gain personal satisfaction and feel greater commitment to the company, leading to more productivity.

Some companies organize tree-planting excursions for groups of employees, who can enjoy nature, feel a sense of teamwork, and make a positive impact on the environment. Others offer matching funds for individual employees' charitable donations. And some companies encourage volunteer work.

Susan Hunt Stevens, founder of employee engagement platform WeSpire, sees three growing trends. "One is that we're now seeing a number of companies making employee engagement one of the most important strategic priorities the companies have, putting employees and the importance of employee engagement front and center," she says. "The second thing we're seeing is the increasing acknowledgment of the importance of transforming your company around purpose."

Research shows millennials are demanding to work for companies with a purpose, in order to find their own sense of meaning. Monetary rewards aren't necessarily the best incentive to make people perform better in the workplace; a sense of purpose may be. Employees want to extract meaning from the 40 hours they put into their work week, and they want the personal rewards that come with working hard for a greater good.

The third trend Stevens is seeing is that companies that offer employee engagement programs in corporate social responsibility (CSR) are finding it doesn't work to offer all employees just one CSR opportunity, since everyone is inspired by different things. She anticipates that companies will be offering employees a portfolio of choices, and giving them a voice in CSR programs. "It's empowering for employees to feed the ideas that really resonate, or to be leaders of the programs that drive the business," she says.

WeSpire is an online platform where employees can find and participate in social and environmental programs the company has activated. The platform uses game mechanics to recognize progress, like earning a Droughtbusters badge for taking actions that save water. There are also Facebook-like features so employees can encourage their colleagues by commenting on and liking actions. Users can choose their interests, set up achievement goals, track their progress, and see their personal contribution to team results. The website can run and download reports, calculate ROI, identify usage trends and recognize leaders.

WeSpire isn't the only employee engagement app. Others include Tap My Back, Cool Choices, which is organized like a card game, and Live Goode.

WeSpire publishes an annual research report on the evolution of employee engagement, and this year's results highlight three keys to successful employee engagement:

1. Effective Management. The first is having good managers. In WeSpire's survey of 413 employees, 89% of very engaged employees feel like their manager cares about them.

2. Transparency. Companies that clearly share information on their goals and impact give employees the sense of purpose they desire. The report says that "this sense of shared purpose is crucial, especially for younger generations."

3. Choice and collaboration. Employees like to choose what programs to participate in, and they want to know about the efforts of the rest of the team. If possible, they like to collaborate with co-workers on projects.

Stevens is excited about the momentum she sees coming from millennials to drive companies toward a more positive social and environmental impact. "Brands that embrace the changes will thrive," she says. "Those that dig their heads in the sand won't survive."