The Environmental Pyramid

A powerful meme in environmental engineering is the pyramid.  I first encountered this when I was working on hazardous waste in the 1980’s.  In that context, the pyramid has the more preferable alternatives (e.g. waste prevention) towards the base.  In recent years, the inverted pyramid has become more popular, and I think it more preferable, since it includes the more preferred alternatives on the top.  An example of this in the waste management context is:



This meme has broad utility outside the waste management hierarchy, and integrates well with the general movement towards sustainability.  Let me give two examples.

In water supply when additional sources are needed, this meme might include (going from the top of the inverted pyramid to the bottom):

  • Use reduction (conservation) (most preferred)
  • Internal recycling (e.g. recycling within a building or block — for example, use of cooling water for toilet flushing)
  • System wide reuse (and possible dual supply)
  • Abstraction of water from a new source and treatment

In energy supply, a possible set of hierarchies might be:

  • Demand reduction (conservation, incentives, …)
  • Internal recycling (heat recovery; energy recovery from on-side discarded materials)
  • System wide re-engineering of energy consumptive processes and operations
  • Abstraction of new sources (with ranking based on environmental/sustainability metrics)

Using such memes, in making decisions it should be incumbent on decision makers (and their consultants) to indicate why upper levels of the pyramid might not be feasible, might be too costly, might impose other environmental risks, etc., before proceeding to lower levels of the pyramid.

How do we train/retrain students, practitioners and the public towards this goal?

A Reminder About Why We Care About Air Pollution

Headlines in the last week talk about the record levels of air pollution in Beijing. There is a nice article today in Discovery about how not only can air pollution cause significant human health effects, but can also affect plants, and air and water quality in distant locations.

This is a reminder of and reminiscent of many air pollution episodes that happened in the US of similar severity up to the 1970’s when environmental legislation such as the Clean Air Act kicked in.  Perhaps the most severe and notorious of these was a 1948 incident in Donora, Pennsylvania.  It is unfortunate that developing countries have not learned from the mistakes in developed countries in avoiding massive environmental degradation in the name of so-called development.


(Image from National Library of Medicine)

Can the Good be the Enemy of the Best?

One topic that has been on my mind for a while is the issue of “sunk costs” and potential perverse effects.  Many of the elements of infrastructure (environmental or otherwise) are highly capital intensive.  Having made a particular decision to attack an environmental problem, the spent capital costs act as a deterrent (and perhaps even the technological choice has disincentivized our ability to go down an alternative path which may have even emerged later).  Of course at the time that the decision is made to adopt a particular solution, it may in fact have been the best (and not merely a “good” solution).

I don’t know literature in this area very well and am not sure how this might be approached.  I can think of several areas where clearly this phenomenon has occurred:

  • The use of combined sewers.  HIstorically, as I understand it (at least in some European cities — see The Great Stink of Paris), storm drains pre-existed, while frequently houshold sewerage was allowed to be disposed of in the streets.  When this resulted in odor and health problems, the idea of disposing of sewerage into the storm drains gained hold.  Of course, we now recognize that it would have been better (in terms of avoiding CSO problems, etc.) to construct seperate sewers.  However, having gone the combined sewer option, it has become very expensive to consider retrofitting — imagine having to reconnect every building in a large city!  Newer cities are invariability built out with separate systems.
  • It was once considered standard practice for chemical companies to dispose of their waste (perhaps in drums) in depressions or low lying areas on their property and bury them.  We now recognize, with Love Canal being the early signal example, that this practice (which perhaps was considered acceptable at the time) was really a vast environmental insult and has resulted in multi billion dollars being spent in hazardous waste cleanup.

There may be ongoing situations where such decisions are being made which may make later “best” decisions more difficult.  This is controversial, but it is worth considering a few examples of more recent or current issues:

  • Did the development of the interstate highway system and resulting impacts on patterns of habitation make it more difficult (or even impossible) to develop more sustainable residential and transportation systems?
  • Will the growing use of natural gas as a fossil fuel act to preclude more sustainable and desirable alternatives (because gas is currently considered to be “cheaper” – when externalities are ignored.  See my earlier post on the Commons effect.)

How can we guard against “good” solutions being the enemy of the best.  I don’t know.  Perhaps using concepts of adaptive management can assist. Perhaps implementing solutions on a distributed basis may help.  How do we account for potential transformative changes (which we don’t currently know) that may occur in the future into our current decisions?

I welcome and encourage thoughts and comments on these topics.

Garrett Hardin – Tragedy of the Commons – Key Papers #1

In this post, I will start a series of discussing papers that I regard as influential to environmental engineers (or at least to the areas of environmental engineering that I have devoted attention to).  The first paper I discuss is Garrett Hardin’s paper, “The Tragedy of the Commons”, which was published in Science in 1968.

Garrett Hardin was a professor at the University of California – Santa Barbara, who died in 2003.  Wikipedia has a very nice biography.  1968 was two years before the first Earth Day.  While Hardin’s main objective was to look at the problem of overpopulation, he tackled in his paper the subsidiary problem of why is there pollution.

Hardin’s central metaphor is the idyllic Commons — traditionally a plot of land in a village — in which anyone was free to graze their animals.  It was in the interest of every individual to maximize their use of the Commons (adding animals), yet if everyone behaved in such a manner, the Commons would be ruined beyond its carry capacity.

In economic terms, the negative externality of use of the Commons was not passed back to each individual fostering overexploitation.  Therefore there was no incentive not to overuse the resource.

Analogies to pollution control are abundant – if the ability to dispose into the air, water or soil is treated as a free asset, then there is every incentive to overexploit such asset.

What can be done?  Hardin suggests that, agreed moral coercion in the form of regulations, taxes, or regulation are needed, but he recognizes the inherent conflict between liberty and such strictures.

Hardin wrote a re-examination of the paper in 1998 – 30 years later.  He fundamentally reiterated the main messages, but realized that he perhaps should have titled his paper “Tragedy of the Unmanaged Commons”.  He wrote (in 1998):

Its message is, I think, still true today. Individualism is cherished because it produces freedom, but the gift is conditional: The more the population exceeds the carrying capacity of the environment, the more freedoms must be given up. As cities grow, the freedom to park is restricted by the number of parking meters or fee-charging garages. Traffic is rigidly controlled. On the global scale, nations are abandoning not only the freedom of the seas, but the freedom of the atmosphere, which acts as a common sink for aerial garbage. Yet to come are many other restrictions as the world’s population continues to grow.”

Now, 45 years after the original paper, 15 years after the restatement, and 10 years after Hardin’s death, the message remains true.  Unrestricted exploitation of a commons will inevitably lead to tragedy.  So a central problem of environmental engineers interacting with policy makers is how best to preserve and enhance the assets that a commons presents while using the lightest footprint on individuals.

The Positive Effects of Disasters

Being in San Francisco for the Society for Risk Analysis in early December of 2012, having not been there since the Loma Prieta earthquake in 1989 (yes, I was actually IN the earthquake) gave me a realization that natural disasters can have a silver lining in terms of the footprint of cities. I was staying at the Hyatt one block away from the Ferry Building on the Embarcadero. In 1989, this was an elevated freeway which, like all too many cities (including my current venue of Philadelphia) served as a physical obstacle between people and the waterfront. As nicely documented in Roughly Drafted, the quake demolished the freeway and tipped the balance in favor of those who wanted it gone in the first place.

Years later, the freeway is gone, there is a nice linear walkway in San Fran, and the Ferry Building itself has been transformed into a gourmet mecca (Ferry Building Marketplace)


image from wikipedia – GNU License

Other cities have had major disasters turn into positive planning and development opportunities. The Great Chicago Fire in 1871 (Wikipedia) destroyed much of the city. However, its aftermath provided the opportunity to develop the unique lakefront park belt that we know today (

Are there other examples of spinoff benefits that have occurred in other cities?

What lessons can we learn from this in the reconstruction of shoreline following Superstorm Sandy?