Biogas digester vs gassifier

Hi,

First up, I'm new here, so go easy on me! I stumbled across your site when doing some follow up research after looking for ways to get rid of a huge pile of leaves!

Anyway, I'm keen to go down the whole "off the grid" path and am looking at aqua phonics etc.

My question here involves energy production. I was wondering if anyone could offer some advice.

It seems to me that there are three ways to "consume" the fuel. You can burn it directly (I plan a rocket-stove design), you can digest it to produce methane or you can gasify it to produce another flammable gas (hydrogen?)

I'm looking to use a combination of kitchen scraps, garden waste, wood-workshop waste and possibly human and animal waste as my fuels, but which methods should I use for each in order to get maximum energy?

For example, the leaves and / or grass clippings. Am I better digesting them to get methane, or turning them into pellets and gassifying? Or maybe even just burn directly? If I digest them, can I dry the waste product, pellet it and burn (or even gasify)?

Obviously, some fuels are a no-brainer (I can't imagine gasifying the dog poo!) but advice would be appreciate!

I also plan to store the resulting gasses to power both internal combustion engines and to burn directly. Can the two gasses be safely mixed and stored / used together, or is that a BAD idea?

All advice gratefully received!

Paul Simpson : Welcome to Permies.com, and our sister site Richsoil.com, We follow a 'be nice' policy here at permies, with 28,000 + fellow members
Worldwide, you should be able to come here 24 /7 and find someone who wants to talk about what you want to talk about !

I am only going to take a few small pieces of your post and leave room for other commenters, Rocket stoves are actually a cooking stove used out doors, on patios,
near open doors, ( mostly in bad weather , a few are built with an air gap with a simple chimney above the cooking surface, not unlike a rudimentary Chem lab Fume
-hood ! Because of the extraordinary high working temperatures and its strong draft, the Rocket Mass Heater would be prone to 'inhale' leaf-like materials, which
can result in partial or complete plugging of the horizontal or final Vertical Chimney- filling the house with smoke !

There are several ways to pelletize fuels, most are ether energy or man-hour intense operations and seem to serve a community or small group better than even a
large family.

Hydrogen is our simplest and smallest element, as such it is known as an extremely 'slippery' molecule. It is true that when hydrogen is chilled down to the point that
it becomes liquid, and is then poured into a glass container -the individual hydrogen molecules will leak out through the walls of the Glass container !

It is possible to Store the Methane from a Digester, or even the other flammable gas produced by a Gasifier which is Carbon Monoxide, with due care this gas has
often been stored in The Inner-tube of large tractor tires !

You have an interesting path to travel, keep the questions coming, it is within the off the wall questions that we will find the way forward/back to the future !

Think like Fire! Flow like Gas! Don't be the Marshmallow! As always, your questions and comments are solicited and Welcome! For the Crafts! Big AL

Paul Simpson wrote:It seems to me that there are three ways to "consume" the fuel. You can burn it directly (I plan a rocket-stove design), you can digest it to produce methane or you can gasify it to produce another flammable gas (hydrogen?)

I'm looking to use a combination of kitchen scraps, garden waste, wood-workshop waste and possibly human and animal waste as my fuels, but which methods should I use for each in order to get maximum energy?

Paul, your questions are greater than the title of your topic!

1st question is about diferenciating the "biogasES" beause there are 2 points in the same forum, digest and gasify.
I said before that I was confused and a bit lost....
What are the common points and differences between a gasifier and a TLUD?
May be just that the TLUD is a sort of gasifier, an up-draft one....

You are right that gas can be from 2 techniques:
- they have gas in common, by 2 means
- and right to compare with rocket: there is fire in common with the gasifier!

Am I right to think that fermentation is safer to produce gas for cooking?
And better for stocking?
hehe, cold gas....

Am I right that TLUD are also ok for cooking, but not as safe because of CO (=absolute use outdoor)?

I would really like to understand the differences, advantages and drawbacks.

2nd question, what method for which fuel, super great.
My ideas:
- wet stuff = fermentate (digest)
depends what can be dried easily or not.

- animal and human manure = fermentate if you have a lot.
Don't if you have little, because the bacteria cautions imply more time to secure the side-prodycts of gas.
(there is a topic here about pros and cons of humanure compost toilet or digestion).

Dung can be dried and burned.

- Big pieces of wood: burn in rocket
- little pieces: TLUD or other gasifing device

Then I have unanswered questions about the difference of draft between rocket and gasification....
This can also be a way to chose between the techniques.

Hi, This is an old post, but you could consider the option of composting the leaves to produce hot water and/or household heat. We are currently looking at building variations of both of these models.
http://www.builditsolar.com/Experimental/MbSoft.htm

Biodigesters need a lot of waste, time, and infastrucure to produce enough fuel for a home. It is possible, but needs to be a large stable system, with a large waste stream. Trust me, i would love to build a digester and live off of it. But there's a reason you rarely see it in a homescale version, as a stand alone system, outside of a waste management situation. Great for solving problems, not so great for the sole use of energy production.