An intriguing use of the result of a calculation like this would be to calculate the value of the carbon emissions avoided on the global carbon market (as is done the article cited below). This gives you an instant ability to value the investment of the grant. The cost-benefit analysis is pretty coarse. But if you were reliably promising $20,000 of carbon avoided in the next year, and I were an agency whose job it was to produce public goods via grants, I would gladly trade $10,000 cash for the $20,000 value you were offering (provided I had no better alternatives).
 

Massink, R., Zuidgeest, M., Rijnsburger, J., Sarmiento, O. L., & van Maarseveen, M. (2011). The Climate Value of Cycling. Natural Resources Forum, 35(2), 100-111. doi:10.1111/j.1477-8947.2011.01345.x

The reduction of CO emissions constitutes one of the largest challenges of the current era. Sustainable transportation, and especially cycling, can contribute to the mitigation of CO emissions since cycling possesses an intrinsic zero-emission value. Few studies have been conducted that appraise the CO reduction potential of cycling. Opportunity costs enable the estimation of avoided CO emissions resulting from bicycle trips. The methodology developed in this research allows the attribution of a climate value to cycling by substituting bicycle trips with their most likely alternative transportation modes and calculating the resulting additional CO emissions. The methodology uses data on the current modal shares of cycling mobility, the competition of cycling with other transportation modes, and CO emission factors to calculate the climate value of cycling. When it is assumed that the avoided CO emissions of cycling mobility could be traded on financial carbon markets, the climate value of cycling represents a monetary value. Application of the methodology to the case of Bogotá, Colombia - a city with a current bicycle modal share of 3.3% on a total of 10 million daily trips - results in a climate value of cycling of 55,115 tons of CO per year, corresponding to an economic value of between 1 and 7 million US dollars when traded on the carbon market.