In anticipation of Earth Day, we’re celebrating the Echoing Green Fellows solving the world’s biggest environmental problems. From food systems to climate change, green technology to sanitation, here are seven powerful updates from the field.

2002 Echoing Green Fellow Ian Marvy launched Added Value to empower the youth of South Brooklyn to develop new skills and positively engage with their community through the operation of a socially responsible urban farming enterprise. Added Value was awarded a 2012 Edible Brooklyn Local Hero Awards, for “changing the way people eat in parts of the borough that need it most.”

Sanergy, founded by 2011 Echoing Green Fellows David Auerbach and Ani Vallabhaneni, resolves the massive sanitation problems in Africa’s slums with a network of clean, containerized toilets and service to convert the waste to electricity and organic fertilizer. A few weeks ago, Sanergy installed their first “Fresh Life Toilet” and shower in the maternity ward of a medical clinic in Kenya.

2011 Echoing Green Fellows Brenden Millstein and Raphael Rosen founded Carbon Lighthouse to take on global climate change at a meaningful scale by building a one-stop-shop for companies to eliminate their entire carbon footprint. Carbon Lighthouse engineers recently conducted energy studies at 52 schools in rural Oregon and uncovered more than $2.5 million in possible energy savings.

Green Coast Enterprises, founded by 2008 Echoing Green Fellows William Bradshaw and Reuben Teague, builds environmentally sound and affordable structures in the Gulf Coast, with a special focus on coastal areas threatened by climate change. Green Coast Enterprises is working on an $8 million development called HUB NOLA, which will serve as an incubator and creative workspace for New Orleans social entrepreneurs.

A Single Drop for Safe Water, founded by 2007 Echoing Green Fellows Gemma Bulos and Kevin Lee, develops safe water systems in villages across the Philippines through the combination of low-cost water purification technology and local community ownership. A Single Drop for Safe Water recently started construction—employing 50,000 local residents—on the first government-run water system in Parang, a municipality in the Phillippines.

Founded by 2008 Echoing Green Fellows Andrew Butcher and Chris Koch, GTECH reclaims vacant land through the growth of alternative energy crops, meanwhile serving as a platform for green job training. GTECH was recently named the grand prize winner of The Sprout Fund for their efforts to collect used cooking oil in order to provide feedstock for biodiesel production in Pittsburgh.

2010 Echoing Green Fellow Jason Aramburu launched re:char, which distributes carbon-negative power plants that produce energy from waste and replenish soils in rural farming villages in the developing world. re:char recently launched Black Revolution, the world’s first carbon-negative replacement for potting soil. Mashable.com recently interviewed Jason about his work in Africa:

Explore more Echoing Green Fellows working on environmental issues.