Got questions? Ask the Green Geek.

Green Geek LogoWondering if you need to take the lids off when you recycle those plastic bottles? How to cut back on your driving? Or if aluminum is “greener” than plastic? 

Ask the Green Geek.

Pima County FYI has a monthly column featuring questions and answers on all things green. Our own Green Geek gets assistance on answering your questions from the sustainability experts in Pima County’s Office of Sustainability and Conservation.

Send your questions to And look for the column the second Friday of each month on the left sidebar of the newsletter.

Here are this month’s questions: 

Dear Green Geek,

When you recycle plastic bottles, should you take the lids off? If so, why?
Thank you!


Hi, Jeff, 

Great question. It really depends on the recycling facility, but it’s a safer bet to throw the lids away. Here’s why: 

Caps, tops, and lids are not typically made of the same kinds of plastics as their containers. When two types of plastics are mixed, it’s often considered contamination, which reduces the value of the material or requires additional resources to separate them before processing. 

Caps and lids can jam processing equipment at recycling facilities and plastic bottles with their tops still on may not compact properly during the recycling process.
They are a potential safety risk for recycling facility workers. Most plastic bottles are baled for transport and if they don’t crack when baled, the ones with tightly fastened lids can explode when the temperature increases.

Hope this helps!
Green Geek

Dear Green Geek,

I know people say driving your car is bad for the environment, but I live across town from my office. What are my alternatives?


Confused Commuter

Hello, Fellow Commuter!

Thanks for asking. All our driving is putting about half the air pollution into the air we breathe, adds nearly 40 percent of greenhouse gases into the atmosphere, contributes to stormwater pollution and is costing us a pretty penny. Owning and operating a personal vehicle likely costs $4,000 or more per year. 

You can shave your driving expenses by simply driving less and incorporating efficiency measures into your driving style. For example:
  • Keep tires properly inflated
  • Check and change air filter regularly
  • Accelerate and drive smoothly
  • Avoid jackrabbit starts
  • Avoid vehicle idling
  • Combine errands into one trip - a "cold" start consumes more fuel than restarting a warm engine
You also can think about ways you can drive less:
  • Walk, bus, or bike to school, work, and for errands
  • Share rides with friends (carpool/vanpool)
  • Plan your route so you'll make fewer left-hand turns
  • Combine errands into one trip so you don't have to go out again
  • Avoid unnecessary driving - phone ahead to confirm store hours or product availability
Happy Commuting
Green Geek

Dear Green Geek, Water containers

Is it greener to buy drinks in an aluminum can or in a plastic bottle? 


Hi, John,

The answer to this question is nuanced and ultimately inconclusive. Without knowing all of the factors that go into the life cycle of both plastic bottles and canned drinks, such as the distance these products traveled between its production and consumption and whether it is recycled or not, there is no clear-cut winner. Plastic bottles and aluminum cans have environmental drawbacks and benefits when compared to each other:

Environmental impacts from production:  

Mining bauxite ore, refining it into aluminum oxide, manipulating it into sheets of aluminum, and then manufacturing them into aluminum cans involves considerable amounts of energy, environmental disturbance, and transportation from extraction of resources to processing material into a can. Carbon dioxide emissions from manufacture alone is approximately 1,568 g per six-pack of cans.

PET (polyethylene terephthalate), whose production involves making pellets from petroleum derivatives and then blow-molding the bottles. Carbon dioxide emissions from manufacture alone is approximately 825 g per 2-liter bottle, which holds about the same amount of liquid as a six-pack of cans. 

Plastic bottle production contains petroleum, but aluminum can production uses more energy, emits more carbon dioxide, and is more complicated to manufacture.

Assuming that both beverage containers are filled in the same facility and shipped to the store with the same truck, the plastic bottle weighs 2.05 kg when full (2 liters plus 50 g) and the 5.6 cans weigh 2.084 kg (2 liters plus 84 g). This means that the cans require slightly more fuel to transport than the bottles.

Aluminum recycling is a very efficient process—manufacturers can melt down and reuse aluminum from reclaimed containers repeatedly with little loss in quality. According to The Aluminum Association, creating an aluminum can out of recycled materials requires only 5 percent as much energy as creating a brand new can from bauxite ore. 

Widely used in drink containers, PET is recycled into products like carpeting and jackets. It takes about 1/10th as much energy to recycle plastics as it does to create plastic from raw materials. However, due to alterations in the chemical structure during the recycling process, many plastics become different types of products once recycled.

Thus, producing cans from recycled aluminum takes less energy and is a simpler process, but recycling plastic bottles can result in a wider range of products. 

While there is no clear answer on which material is better for the environment, there is a consensus on what you should do after using a can or plastic bottle: recycle it!

Green Geek
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