Cow Carbon Holds a Key to Our Waste Problem
Cows and other cud-chewing livestock are to blame for the majority of agriculture’s greenhouse gas emissions. Instead of focusing on this issue, let’s explore how the gas is created and how it can help fight the climate crisis by turning our organic waste into renewable energy.
Before we go any further, let’s dispel a common misconception. Cows do not have four stomachs. They do have a four-compartment digestive system though. This is the same digestive system as all ruminant livestock, which allows them to digest fibrous plants through a process known as anaerobic digestion (AD).
AD is a natural process that takes place when organic material hangs out in an oxygen-free zone. Methane is a byproduct of AD, which is why environmentalists and scientists tell us to reduce our beef and dairy consumption. But what if we could capture that methane and use it as a fuel source?
Waste-to-value AD plants do just this. By mimicking the process that occurs in ruminants, organic waste including animal waste, crop residues, agro-Industrial waste, sewage treatment, and organic municipal solid waste is converted into biogas and fertilizer.
What Organic Waste Problem?
When you think about climate change, your kitchen waste probably isn’t the first thing that comes to mind. Apple cores and eggshells are compostable, right?
Composting is a great way to cut back on what we rely on our local governments to manage. I share how I’m embracing it on episode 24 of the Bigger Than Us podcast. While composting is a great tool we can all use to be more sustainable, not everyone is equipped to do it at home and municipal composting infrastructure isn’t ready for all of our organic waste. Ultimately, it’s one corner of the big picture.
According to the EPA, the United States alone generates over 40 million tons of food waste. That’s 15.2% of the nation’s total municipal solid waste (MSW). Less than 7% is composted. Instead, a majority ends up in landfills. Without airflow, AD of organic waste takes place slowly, resulting in landfill gas (LFG).
LFG is a viable resource for methane collection. LFG energy projects are on top of this potential, capturing and converting the gasses into heat, electricity and vehicle fuel. Talk about turning trash into treasure!
Composting and landfills are pieces of the waste solution puzzle, but they do have downsides.
- They require a lot of space.
- Groundwater contamination can occur.
- Waste transportation is costly for local governments.
- Their pace can’t keep up with our waste production.
Incineration has long been turned to as a solution to these issues.
Incineration Isn’t the Only Answer for Organics
Incinerating waste reduces its volume by up to 90%, greatly reducing the issues associated with landfills and waste management. Its true incineration is extremely efficient and even generates energy, but it does produce smoke that pollutes the environment.
Let’s not forget that we should look at waste management holistically. In the case of organic waste, this means embracing AD plants.
Anaerobic Digestion: Waste-to-Value
We’ve taken a look at LFG energy projects that turn our landfill problem into a solution, and the pros and cons of incineration. AD plants are a happy medium that works faster than LFG energy projects and runs cleaner than incineration.
Now let’s take a quick look at the ruminant digestive system that AD plant technology models after to get the most out of the process.
Of course, biology is complex, so this is simplified. But, it helps paint the picture.
When cows take a bite of feed, they swallow before it’s fully chewed. Depending on the type of feed, it goes to their rumen or reticulum. In this oxygen-free environment, microbes work their magic and ferment the feed. Once cows are full, their food comes back up so they can process it further. For them, this means chewing their cud. It also results in the release of methane gas—those pesky cow burps we keep hearing about.
Next, the cow swallows and the cud is sent to the omasum and abomasum. These final two compartments absorb water and house enzymes that further break down materials. The “end” result is digestate (manure).
When done on the large scale and controlled environment of AD plants, organic waste is pretreated, then sent to an oxygen-free chamber where fermentation takes place. Moisture, temperature, and pH are carefully controlled, and the mixture is stirred to prevent settling. Carbohydrates, proteins, and fats that make up organic matter get broken down into fatty acids and sugars. These components break down even further into gas byproduct, or biogas. The leftover solid byproduct is the digestate.
Biogas is captured and can be distributed for heat or converted to electricity or liquid fuel. Digestate is rich in nitrogen and nutrients and can be pasteurized and used as a biofertilizer. These byproducts that could be a problem now have many valuable uses that can reduce our reliance on nonrenewable energy.
Feedstock: What Goes In Must Come Out
As mentioned, rumens are cud-chewing creatures. The chewing is so important, they do it twice! This hints at the importance of knowing and treating your feedstock. As my colleague Ben Hubbard said:
“Feedstock is the catalyst that drives all other components of the waste-to-value project development lifecycle.”
Check out Ben’s article for helpful insights and a feedstock matrix to help you plan for your AD plant’s success.
Anaerobic Digestion is Only Part of the Solution
Faster than composting, carbon-neutral and hungry for more, AD plants serve as one long-term solution to our waste problem. Let’s keep in mind that there’s a whole world of waste out there, and AD is only right for the organic type. It’s also slower than incineration, and depending on your feedstock, water consumption may be an issue. This is why it’s important to consider all options—the new, the natural, and the conventional. In my next articles, we’ll continue our journey to explore options for waste-to-value solutions.
At Nexus PMG, we believe that converting waste to value is the new generation of waste management. Learn about our waste-to-value projects.