Tuesday, April 11, 2017

Environmental Impacts of Construction: Photos from San Francisco's Building Boom

My co-author Jae-ho Pyeon and I are putting the finishing touches on a draft manuscript that we've been working on titled "Analyzing the Potential of Hybrid and Electric Off-Road Equipment in Reducing Carbon Emissions from Construction Industries."  This manuscript is the result of a project sponsored by the US Department of Transportation.  (The DOT builds and funds a lot of highway construction, and apparently this explains their interest in this topic.)

In the course of carrying out this research I've learned a lot about construction equipment and this has at times made me feel like a kid playing in the sandbox again.  In addition this project has raised as many questions for me about urban air pollution as we have answered, and I plan to keep studying construction topics.  In this post, I am sharing some observations, questions and photos from walks I've taken around construction sites in San Francisco.  Next month, I will post the draft manuscript.

The timing of this project was interesting as San Francisco is in the midst of a building boom.  Projects including both buildings and transportation infrastructure, including San Francisco's new tallest building, and roadway and subway projects

I begin with the tallest.  The Salesforce tower is nearing completion.  The previous link (and this one) contain excellent images of the tower and views from the top.  My photo below shows the view from the ground.  Note the prominently displayed "Clean Power Tier IV" generator.  Tier IV means it complies with the federal government's most stringent standards for new diesel engines, which emit dramatically lower levels of participate matter and oxides of nitrogen compared to earlier Tiers and, especially, models from unregulated years.

To my nose, the air smelled pretty good there, for a construction site at least.  

Alas, there are only so many Tier IV generators to go around.  The next picture is a street scene and on the right a low-rise condo building is going up.  It is a bit hard to make out, but if you look closely you will see a generator on the right.  If you look even harder you will see the exhaust pipe, which attempts to release the emissions above the heads of people walking by.  I couldn't determine which tier of engine this generator had, but my nose told me it was not the highest.  There is a similarly sized building going up a block away.  Despite having the same exhaust pipe set up, the emissions are noticeable at both sites.  

Why do construction firms use diesel powered generators to generate electricity when (as the picture above clearly shows) grid power is available right over head?  Getting construction firms to tap into the grid has long been recognized as a way of reducing the public health impact of construction, but even in liberal San Francisco it is not a widespread practice

In addition to generator emissions, the other source of emissions from construction that was most noticeable to me on my walks was from delivery trucks coming and go, and also from idling.  The truck in the picture below appeared to be delivering (or perhaps picking up) scaffolding.  However in the several minutes that passed from the time the truck showed up until it was actually able to enter the site, it emitted pollutants noticeable to me, standing about 100 feet away.  Construction firms do try to limit idling but it is a classic moral hazard problem--the operators enjoy a bit more comfort in the cabin with a heater on, and they save a few calories of energy from having to turn the engine off and on again, but the construction firms lose money on wasted energy.  And of course the public suffers exhaust externalities.

Turning now to transportation infrastructure, the picture below shows a Cat excavator.  It is hard to make out the model number but it looks like a 345B.  The current edition of the Caterpiller Performance Handbook lists a 345D, which comes in a Tier 2 and a Tier 3 version.  Thus this would not appear to be one of the cleanest models, despite the fact that it is working on a tunnel (though it is above it, not in it.)

For work in tunnels and indoor applications, equipment manufacturers have developed electric powered excavators.  In fact electric equipment has long been used in mining and we've seen examples of plug-in excavators and trolley-line powered dumpers.  

Recently, advances in battery technology has opened up the possibility of battery-powered electric equipment.  For example the Takeuchi e135, marketed as the Green Machine, has recently become available in the United States.  But like with substituting diesel generators for grid electricity, a question remains of how construction firms will recharge their equipment if certain factors make it difficult or undesirable to tap into the grid on job sites.

The final picture below is of another transportation improvement project.  The Van Ness Bus Rapid Transit project is the first of its kind in San Francisco.  This project has elements of a roadway improvement as well as public transit, and "BRT" is one of the transit technologies that has gained prominence around the world in the last decade.

The excavator here is a Cat 311D.  I believe this is a Tier 3 machine.  It is not as big as the one used in the Central Subway project, and battery-powered versions of it will soon be available that could handle this job.  But again the question remains how will it be recharged?  There are overhead lines (visible in the picture, which power a trolley bus line; San Francisco along with a small handful of other cities, has long had electric buses powered by overhead lines) so it would seem technological feasibility is not the problem.  Instead there are likely to be "institutional" factors that are slowing the development and adoption of electric equipment.

Finally, it is important to note, and we address this in our research, electric power is not always greener than diesel.  For example, recent economics research has shown that in some states electric cars are actually worse (for the environment and public health) than gasoline powered automobiles. As the US electricity industry switches from coal to greener sources of electricity, the environmental case for electric equipment will strengthen but in the short run it is important to realize that the use of electric equipment may not always be good for society.

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