The implementation and management of various eco-projects also matter a lot. Among the various recent articles in Financial Times is one that describes the ongoing failure of the methane recovery systems from pig manure in Mexico. I've mentioned the various successes in South Asia and elsewhere with these systems. They are very important in many developing countries. The technology itself was shown to work in Mexico, with a few successful systems. But, construction quality problems, intertie and related problems wth the electrical grid, and other management problems have resulted in most of the systems not working.
There has been a similar shift in the small locomotive industry. The Green Goat hybrid locomotives have run into serious problems. A problem with the batteries led to a major recall that drove the manufacturer into bankruptcy. They've since been purchased and may recover, but genset locomotives have taken 2/3 of the market. The hybrid approach of batteries and one large engine is not superior to the approach of having 3 smaller engines and only running as many as are needed.
In both cases the concept was sound, but you need good management and implementation as well.