As for me - I really focus on 2 issues - recycling and energy savings.
For the first, I develop a program and get the employees involved in the program. At my last employer, I held a contest to see which department could recycle the most materials. At the end, everyone won a cookout by the facilities department and 3 departments won special goodie bags. The amount spent for the entire project (including the grill purchase) was paid back in 2 months due to the reduction in trash services. We went from 2- 8 yard dumpsters 2x per week to 1-8yard dumpster 2x per week.
On the energy savings - I monitored the usage of the building to determine peak loads (we were a manufacturing facility) and we evened out the use to reduce the load. We also kept energy efficiency in mind in any projects we performed. This included going to a tankless water heater system as well as installing variable motors on the cooling tower when the old equipment showed signs of failing. We did not have full cost savings on the tankless water system, however, initial information showed:
* The cost of the 100 gallon tank was approximately $7,000 to be installed. The tank was past its life expectancy and had to be replaced. ROI was based off of the difference between the 2 options - $500
* The cost of the tankless system and installed was $7,500.
* Energy efficiency was approximately 70% of the energy produced to heat the water was being used. With the tankless system, approximately 90%+ of the energy used was going to heat the water.
* In the summer months, the only heating costs come from the heating of water. We noticed our heating costs was decreased by 50% and , suprisingly enough, water consumption also decreased by 20%. We did not get hard numbers yet, because I wanted to compare 12 months of data under the new system to see exactly what was saved.
ROI was approximately 2 months.