12/15/2011 03:24 pm ET | Updated Feb 06, 2012

A Back of the Napkin Plan to Run NYC Garbage Trucks on Restaurant Waste Oil

The NYC Department of Sanitation will use 10 million gallons of fuel, at a cost of approximately 40 million dollars, to collect and dispose of 3.2 million tons of residential waste, in 2011.

I've come up with a simple idea to reduce the cost, of collecting this waste, to zero. I have done a simple back of the napkin calculation to assess its viability, which I would like to share with you.

Before I present a vision of a more sustainable urban future, let's first take a step into the past. The year is 1889, we are in Paris, and structural engineer Gustav Eiffel, has just completed his temporary tower for the World's Fair. Another engineering genius, Rudolf Diesel, publicly demonstrates his high compression engine that is 500% more efficient, than the steam engine it is designed to replace. When he shows the world what he has just spent the last 13 years of his life working on, he uses peanut oil for fuel.

Now back to the future. Although modern diesel engines have improved over the last 112 years, they still work on the same principal; and they all can run on vegetable oil.

This is what led to the insight to make NYC more sustainable. Here's the idea: Fuel the entire fleet of NYC sanitation trucks with used restaurant waste oil. Waste oil as fuel source for waste management.

This is why I think it can work.

According to the NYC Department of Health there are 24,000 restaurants in NYC. This number includes coffee shops, which don't have fryers. Let's assume that 20% of food establishments are coffee shops. This leaves us with 20,000 restaurants that do have fryers. These food establishments range from restaurants that have one lightly used 5 gallon fryer that needs to be changed weekly, to burger joints that have multiple fryers that need to be changed daily.
Restaurant fryer waste oil is an available and untapped fuel source; the question then becomes how much is available?

We know, that the average amount of oil a NYC restaurant uses is somewhere between a restaurant that does a lot of frying and changes its oil daily, and one that uses less oil and changes its oil weekly. If we use a conservative estimate between the extremes we come up with an average of 10 gallons a week per restaurant. If we multiply 10 (gallons a week) by 20,000 (restaurants) and then multiply the result by 52 (weeks in a year), we get 10 million gallons of restaurant waste oil that can be used for fuel per year.

We can use similar reasoning to figure out how much fuel is needed to run the garbage trucks. The Department of Sanitation has a total of 5,600 vehicles in its fleet, 2,230 of them are collection trucks. The trucks are powered by 4 MPG diesel engine workhorses. The department doesn't breakdown their fuel use by vehicle type, but since we know the collection trucks are low mileage as well as the total fuel necessary for the whole fleet, we can assume that even though the collection trucks are about half of the entire fleet, they use more than half of the fuel. So let's say they use 75% of the fuel. This would be 7.5 million gallons a year. It looks like we have more than enough fuel from restaurant waste to power the garbage trucks.

Now here is where it comes together. All NYC garbage trucks are stationed in depots. Which means, the used restaurant oil has to be brought to just a few central locations. This solves a distribution problem, that would make doing the same thing with the taxi fleet (hint, hint) more difficult.

Collection, shouldn't be a problem. The oil that the restaurants use is currently disposed of as waste and is already being picked up by private carters. In order to use the fuel, the restaurant oil only has to be filtered so that no pieces of tempura, or french fries clog the fuel lines.

While admittedly, this is a back of the napkin calculation, it is based on accurate numbers provided by the city, and seems viable. Since it's not every day that an urban idea makes economic sense, environmental sense and also has public health benefits, I think this warrants that NYC should take the next step and explore how to set up a trial in one depot, and based on the results, expand from there. 

The only real disadvantage that I foresee is that garbage truck exhaust will start to smell like french fries and this will make people stuck behind one crave fried carbs. So while, this will make NYC more sustainable and save the city 40 million in fuel a year, it might be in conflict with some of the mayor's other public health initiatives. But I think the trade off is well worth it, I really do.