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Amy Quinton: Hey, Kat. We haven't yet talked about one of the largest sources of greenhouse gas emissions. 

Kat Kerlin: You must be talking about energy. Yep. And specifically, the energy it takes to produce heat and electricity worldwide. 

Kat Kerlin: That's something like a quarter of all emissions. 

Amy Quinton: But there's a silver lining when it comes to the energy sector, particularly here in the U.S. I learned that from Alissa Kendall. She's a professor of civil and environmental engineering here at �鶹��ý. 

Alissa Kendall: Our electricity sector is one of the sectors that we are actually decarbonizing, albeit not quickly enough. But we are able to replace fossil fuels with renewables. So we have replaced a lot of coal-fired power plants with natural gas-fired power plants. Natural gas still has a lot of greenhouse gas emissions, but per unit of energy generated, it's a lot less than coal. 

Kat Kerlin: And speaking of coal, this year, for the first time on record, the U.S. is now producing more electricity from renewable power than from coal. 

Amy Quinton: That's right. Electric utilities are retiring aging coal plants. And, well, the pandemic has pushed coal production into a deep crisis with reduced electricity use and the economic downturn. 

Kat Kerlin: But that's good news for the climate, as coal is the dirtiest of all fossil fuels. 

Amy Quinton: And even if coal makes a rebound, major utilities and technology companies are increasingly turning to renewables. 

Kat Kerlin: In part, that's because renewables are cheaper than coal. Yeah, but there's a lot to unfold when looking at our energy future. 

Amy Quinton: And Alissa is going to help explain it all in this brief bonus episode of Unfold. 

Theme: Climate models all agree that temperatures are going to increase. It's going to be hotter. It's going to be drier. Fires going to burn more frequently. Maybe this is never going to be the way it was again. We need to come up with ways to literally pull CO2 out of the atmosphere. How are we going to work together to solve a challenge like climate change? 

Amy Quinton: Coming to you from our closet studios as we shelter in place across the Sacramento region, this is Unfold, a �鶹��ý podcast that breaks down complicated problems and discusses solutions. 

Amy Quinton: This week, we unfold “decarbonizing energy.” I'm Amy Quinton. 

Kat Kerlin: And I'm Kat Kerlin. 

Amy Quinton: So, Kat, guess what, the biggest problem is when trying to decarbonize the energy sector and rely more on renewables?

Kat Kerlin: The fossil fuel industry lobby? 

Amy Quinton: Likely, yes. But technically speaking, Alissa says there's a big drawback to most renewable power right now. 

Alissa Kendall: The problem with electricity is that at a certain point, it becomes very hard to get rid of our natural gas-fired power plants or our coal-fired power plants if they're still around, because we need some source of very reliable electricity. 

Kat Kerlin: Renewables like wind and solar aren't as reliable because, well, the sun doesn't shine all the time and the wind doesn't blow all the time. So we have this intermittent power conundrum. Right. 

Amy Quinton: Important to point out here, though, that a UC Irvine study found that solar and wind could meet 80 percent of U.S. electricity demand. But like Alissa said, it's that last little bit that is a giant hurdle and requires substantial investment. 

Kat Kerlin: But wait, Amy, aren't we finding ways to store energy from renewables so we don't have to worry about intermittent power... like big batteries? 

Amy Quinton: Well, that's what I thought. But while we can store renewable energy with batteries, it's not for as long as we might need. Alissa says when we start looking at storing it reliably for the grid for extended periods of time - let's say a few weeks of sunless skies - batteries aren't a great option. 

Alissa Kendall: If we think about investing large amounts of money and materials, which would have environmental impacts of their own, if we think about investing all of those to build enough storage capacity to meet these sort of extended gaps in renewables, the economics don't pan out and the environmental impacts don't always pan out either, meaning we might be increasing environmental impacts by investing in a huge amount of battery storage. 

Kat Kerlin: So batteries have a big environmental impact. 

Amy Quinton: Lithium ion batteries require lithium, obviously, but they also require heavy metals like cobalt and nickel and mining. 

Kat Kerlin: Those materials can cause all sorts of pollution problems. We don't want to solve one problem by creating another. 

Amy Quinton: It's interesting you said that because Alissa mainly analyzes the full lifecycle of products, technologies and even policies. And she says it's really critical that we do this. 

Kat Kerlin: That makes sense, because if you think about this on a broader scale, we don't want to just reduce greenhouse gas emissions to fight global warming. We want to improve the environment for everyone. 

Amy Quinton: Alissa became interested in life-cycle analysis when she was just a 22-year-old engineer working in the auto industry, and she worked on some of the very first electric vehicles on the market. 

Alissa Kendall: I also lived right near a coal fired-power plant in Michigan, and the vehicles we were designing at the time were not very efficient. And I kept thinking, are we really helping the environment?  At the time most of us were a lot more concerned with air quality from vehicles than we were with climate change. But still, the question was, are we really doing better? So I thought I invented this new way of looking at the issue. Right? 

Amy Quinton: So like all good engineers, she went to work figuring it out. 

Alissa Kendall: I sat down to try to pencil out like, well, what do the emissions really look like from this vehicle that we're designing? And in the conditions that we were operating in, the gasoline vehicle was much better.