Food and energy

Project Drawdown's breakdown of sources of $CO_2$ (equivalent) emissions:

Food/Agriculture/Land Use ~tied with electricity??

Wait a second...
The energy that makes plants grow (through photosynthesis) is from sunlight. Sunlight is *free* and does not generate any $CO_2$ emissions.

Plants are "carbohydrates": They are full of complex chemicals containing carbon, hydrogen, oxygen, and many others in smaller amounts. But where do they get their carbon from??

From the atmosphere!

So we (animals too)...

1. Eat plants,
2. exhale carbon-dioxide into the atmosphere,
3. But then plants take this carbon-dioxide out of the atmosphere.

So, we are part of "the carbon cycle". And the carbon we take in ultimately comes (via plants) from the atmosphere. So what we breathe out is just carbon-dioxide that used to be in the atmosphere already, and we're just putting it back... End of story!

In the developed world, it takes energy, [usually energy from fossil fuels], in addition to free sunlight energy to grow and process food:

harvesting and farm machinery


transportation


inspection and regulation



Many farms do use manure as a fertilizer--from pigs. (In traditional Chinese agriculture from humans. See also humanure, a recent movement.)

But more common in this country are chemical fertilizers, which require fossil fuel inputs. So do pesticides and herbicides.

Clearing forests for pastureland--land use change--does not consume energy, but it does release the carbon stored in trees back into the atmosphere.

These uses of fossil fuels have made it possible for a few people to produce food for many--and for most of you to consider a career other than agriculture!

We can eat plant food directly,

Or plant food can be fed to animals, and we eat the animals and other animal products.

Much of the energy from the food that they eat goes to daily life needs (like our 2000 Calories / day), and not directly to protein.

Understanding the differences between animal proteins in terms of energy

Feed / food contains Calories--energy.

The Feed Conversion Ratio is $$\text{FCR}=\frac{\text{mass of feed}}{\text{mass of protein produced}}$$ This is a unit-less quantity.

FCR = 2 means that an animal needs to eat 2 kg of feed in order to produce 1 kg of protein. (Protein in the form of meat, mostly. Or in some cases, some other form of protein like eggs or milk...)

1.) If you're going to eat meat, and want to have the lowest environmental impact, should you eat high FCR or low FCR protein?

2.) Does methane contain chemical energy that can be released through combustion? (That is...does it *burn*?)

Let's say that:

1. One kind of animal eats food (energy calories) and grows (produces protein) plus makes some methane gas.
2. Another kind of animal eats food and grows, but produces no methane gas.

3.) Therefore, do animals that make methane as well as protein require more or less energy to make 1 kg protein than animals that don't make methane?

4.) Which kind of animals need to spend more (or less) energy each day just to stand around--that is support their weight against the pull of gravity? And which kind of animal requires the least energy to "fight" gravity?

Cows are amazing!

University of MN, extension service

• 4 compartments in a cow's digestive tract
• #1 - the rumen is the largest, holding up to 25 gallons
• The rumen is a large fermentation vat. Bacteria generate gases: 30 to 50 quarts / hour during digestion. (Alcohol? Surprisingly little. Rather, volatile fatty acids and methane...)
• #4 - the abomasum is the only one that works like our stomachs: glands produce hydrochloric acid (stomach acid) to be mixed with food.

Environmental impacts of food production

Here is the 'Our world in data' breakdown of where in the food cycle emissions are coming from, for many different foods:

tiny.cc/foodimpact

In addition to greenhouse gas emissions, food production has these other major environmental impacts:

Bacteria

Bacteria break down--or "eat"--organic matter and they play a role in food / ag / land use as well. Bacteria that live in oxygen-rich environments--where they are in contact with Earth's atmosphere--tend to emit $CO_2$ as they work. Those that live in oxygen-poor environments emit primarily methane, $CH_4$.

environment	oxygen-rich: aerobic	oxygen-poor: anaerobic
example habitats	soil surface; above ground; compost piles	flooded rice fields (under water); underground; buried in a landfill; in one of several of a cow's stomachs
metabolic byproduct	$CO_2$	$CH_4$
global warming potential (GWP)	1	~32

Hannah Ritchie (Our World in Data) argues that to reduce your carbon footprint from food you should...Focus on what you eat, not whether your food is local.

Salmon Farm Science, MTSOfan, Raymond Clarke Images, USD Agriculture, The Digital Dropout, Ruocaled, Alistair Paterson, Lino Petito, Weitz.com Twisted Times, A Pattern Language... by Christopher Alexander, Forest Stewardship Notes