Engineering Green-Gray Analysis

Colors matter for engineers.  Many engineers face employment concerns relating to our current budget woes.  Our "red-blue" 50-50 stratification has produced political gridlock.  Many engineers are facing furloughs and job uncertainty because of colors.

An equally important color combination for engineering and policy makers is green-gray.  Green in this case is the "green" associated with many of our more pressing sustainability issues and solutions  - - from energy to public transportation to stormwater management.  The "gray"is the color of our engineering past - - concrete parking lots, streets, and bridges.  In many cases "gray-green" may become the primary colors for engineering.  Our public infrastructure is headed down the road of hybrid solutions.  Green solutions combined with the traditional gray (Gray is not a primary color, so the combined color will be something like an olive green.) will be a huge step down the sustainability path.  Olive green will produce huge opportunities for engineers - - just like a little "political purple" would make a large segment of engineers sleep better at night.

This article by Tailberth, Gray, Yonavjok, and Gartner Green versus Gray: Nature's Solutions to Infrastructure Demands is a good primer on the green-gray infrastructure analysis.

From the introduction to the article:

"Substitution of nature’s services with technological alternatives has been pursued with almost religious zeal as societies have industrialized over the past three centuries. But the time for reverse substitution may be upon us. In a wide variety of settings, from water purification to climate change adaptation, investors are increasingly considering the worthiness of green infrastructure solutions, such as mangrove restoration, rather than conventional gray investments, such as sea walls, to achieve the same environmental quality outcomes. But in times of fiscal austerity, cost-effectiveness is paramount. The problem is that infrastructure investors do not have a consistent and robust way to compare gray with green infrastructure in an apples-to-apples manner that is convincing to budget hawks. In addition, uncertainty is greater with “unproven” green infrastructure approaches. As a result, green solutions are often neglected. Here, we present the contours of a general methodology called green-gray analysis (GGA) and demonstrate its usefulness in a green-gray trade-off facing the Portland Water District in Maine. Results provide evidence for the superiority of green investments in several scenarios, purely on financial terms. When ancillary benefits, such as carbon sequestration or passive-use values for Atlantic salmon are factored in, the case becomes even more compelling. A replicable GGA methodology can be one important solution for scaling up green infrastructure investments worldwide."

Also, three common investment objectives for considering green infrastructure alternatives outlined in the article:

1. "Minimizing the costs of mitigation plus the expected value of losses from natural and human disturbances. Take the example of coastal flooding from storm surge events. Relevant gray investments may include sea walls, dikes, levees, pumping facilities, and floodways. Relevant green infrastructure investments may include restoring mangroves, dunes, and wetlands. In these and other disaster-risk cases, the public investment objective is to reduce the expected value of the loss, which is simply the probability of a disaster or disturbance occurring multiplied by the value of the loss should the event occur.
2. Minimizing the cost of meeting a regulatory or planning objective. Reducing the delivery of nitrogen and phosphorous pollution entering receiving water to a target specified by a wastewater treatment plant’s Clean Water Act permit is one example. The nutrient load target can be achieved by upgrading plant technology or capacity, or by financing best management practices on farms upstream.
3. Maximizing the net public benefits of infrastructure investments. An example is a fisheries management agency seeking ways to enhance high-value recreational fish resources through either investment in hatcheries (gray) or dam removal and stream restoration (green). Importantly, under this objective, all categories of benefits and costs apply, including both market and nonmarket benefits that may be ancillary to the primary infrastructure investment rationale. These ancillary benefits represent an important component in many existing GGA applications and are critical to efficient investment in environmental management. In particular, investment decisions made on the basis of cost alone undervalue additional ecosystem service benefits produced by green infrastructure and hence may lead to suboptimal investment decisions."