<p>Just a general question, I read somewhere that methanogenic bacteria can generate around 415L methane per kg of grass which would yield 16,800 kWh hours per year given a 1 acre yard. Why aren't there systems that use household waste for energy production?</p>
<p>Here are the calculations I  did:</p>
<p><a href="https://www.witpress.com/Secure/elibrary/papers/ESUS11/ESUS11033FU1.pdf" rel="nofollow noreferrer">1kg Grass/m2/year</a> -&gt; 1* 4047m2/acre -&gt; 4047kg grass/year -&gt; 4047kg * <a href="https://www.sciencedirect.com/science/article/abs/pii/S0306261911005435" rel="nofollow noreferrer">415L methane/kg</a> -&gt; 1,679,505L methane -&gt; 1,680 m3 * 10 kWh/m3 -&gt; 16,800 kWh</p>
<p>I know that there are already places that use biogas but wouldn't it be more efficient for a home to directly use this energy from its own waste?</p>

CC BY-SA 4.0
2024-10-28T07:48:42.883Z
I'm not following our calculation.  4047 kg grass per year for a private household?  What private home has 4000 m² of grass?  Reading the title of your question, I thought you wanted to use solid human waste, and at least for domestic heating, [such systems exist](https://en.wikipedia.org/wiki/Compost_heater).  One [could potentially generate electricity](https://www.npr.org/sections/thesalt/2016/04/05/472673127/how-colorado-is-turning-food-waste-into-electricity), but that is much less efficient.
gerrit
CC BY-SA 4.0
2024-10-28T08:17:52.913Z
What type of device/system is needed to convert grass to methane? How much time is required for the conversion? How much energy would such a system use. What would be both the capital & operating costs of such a system? When you have that information compare it to how much methane & energy could be extracted. Then consider what the global market for such a system would, given that most of the world's population doesn't live on 4047 sq meters of grass producing land.
Fred
CC BY-SA 4.0
2024-10-28T15:36:28.360Z
Thanks for your comments. Just to clarify, I’m assuming a house has an acre of yard space which is around average in my town, and the grass clippings from that acre of yard is collected. Additionally, I’m not including food and paper waste which further adds in to the energy potential. To collect the methane, I’m proposing anaerobic digestion from methanogenic bacteria
Aakarsh Tathachar
CC BY-SA 4.0
2024-10-29T09:18:39.000Z
Point #1: Your calculations seem to be more than a bit off. Point #2: Urban and suburban lots in the US, and in many other places, are a quarter of an acre or less, and that includes a house (sometimes a huge McMansion), a patio or deck (or both), a driveway, a garage, a front walk from the street to the house, a home owner association mandated "garden" of some sort. There's not all that much grass on a standard urban or suburban lot. Point #3: Every household has expensive methane capture equipment? This is not realistic.
David Hammen
<biogeochemistry><energy>
Why isn't methane released from decomposing waste in homes being used for electricity production?
Aakarsh Tathachar
# Why isn't methane released from decomposing waste in homes being used for electricity production?

(Asked by: username_0 on 2024-10-28)

Just a general question, I read somewhere that methanogenic bacteria can generate around 415L methane per kg of grass which would yield 16,800 kWh hours per year given a 1 acre yard. Why aren't there systems that use household waste for energy production?

Here are the calculations I did:

[1kg Grass/m2/year](https://www.witpress.com/Secure/elibrary/papers/ESUS11/ESUS11033FU1.pdf) -> 1\* 4047m2/acre -> 4047kg grass/year -> 4047kg \* [415L methane/kg](https://www.sciencedirect.com/science/article/abs/pii/S0306261911005435) -> 1,679,505L methane -> 1,680 m3 \* 10 kWh/m3 -> 16,800 kWh

I know that there are already places that use biogas but wouldn't it be more efficient for a home to directly use this energy from its own waste?

**Tags:** biogeochemistry, energy

> **Comments:**
> **username_1**: I'm not following our calculation.  4047 kg grass per year for a private household?  What private home has 4000 m² of grass?  Reading the title of your question, I thought you wanted to use solid human waste, and at least for domestic heating, [such systems exist](https://en.wikipedia.org/wiki/Compost_heater).  One [could potentially generate electricity](https://www.npr.org/sections/thesalt/2016/04/05/472673127/how-colorado-is-turning-food-waste-into-electricity), but that is much less efficient.  
> **username_2**: What type of device/system is needed to convert grass to methane? How much time is required for the conversion? How much energy would such a system use. What would be both the capital & operating costs of such a system? When you have that information compare it to how much methane & energy could be extracted. Then consider what the global market for such a system would, given that most of the world's population doesn't live on 4047 sq meters of grass producing land.  
> **username_0**: Thanks for your comments. Just to clarify, I’m assuming a house has an acre of yard space which is around average in my town, and the grass clippings from that acre of yard is collected. Additionally, I’m not including food and paper waste which further adds in to the energy potential. To collect the methane, I’m proposing anaerobic digestion from methanogenic bacteria  
> **username_3**: Point #1: Your calculations seem to be more than a bit off. Point #2: Urban and suburban lots in the US, and in many other places, are a quarter of an acre or less, and that includes a house (sometimes a huge McMansion), a patio or deck (or both), a driveway, a garage, a front walk from the street to the house, a home owner association mandated "garden" of some sort. There's not all that much grass on a standard urban or suburban lot. Point #3: Every household has expensive methane capture equipment? This is not realistic.  

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