Biochar from prickly pear?

Hello,

I saw that it is possible to make biogas from prickly pear segments. This was promoted as an ideal biogas material to add because it can be grown with little water. Somewhere else it was mentioned that prickly pear was good for adding carbon to the compost, because it needed little water and thus could be grown on dry barren lands. But, I have tried to pick the fruits but there where lots of spines on it. Small spines which where very hard to get out. And if you'd need to dig in the soil you'd be under the spines. So I tought that it would be usable to make biochar from it after drying. Is this correct? Will the carbonized spines still sting or are they too brittle?

Greetings,

Matis

Burning will remove the spines, especially the small hairlike spines that get stuck under the skin.

Pretty weird then that there are not many people using this.
I know somebody in Turkey and I'm sending her perennial seeds like ají dulce pepper, winged bean, pigeon pea. Perennial permaculture plants.
I'm also going to give her this idea because on the unirrigated plot of her land she has many prickly pear cacti!

Is prickly pear somehow invasive and fast growing in your location? In california I could have faced a very large fine for removing a single pad, there quite endangered and I couldn't imagine a situation where I would turn my gaze upon a cactus as a source of biomass never mind burning it.
I understand in conditions with no tree's let's say carbon can be hard to come by, but when we start ripping out the survivors I can't see a future were we'll ever see a tree again. If you can grow cactuse's would not other arid brush species not grow much faster and produce more biomass. I'm not understanding the strategy because I'm having a hard time creating a condition in which I'm in such an abundance of cactus but nothing else that I'd compost food.

A side note, i had no problem collecting prickly pear and traveling out of country with it in my bag by simply using pieces of paper. I had no gloves, let's just say I was driving back to the airport and decided to hop in a ditch that caught my eye. A few layer of paper in each hand and you can just clap the pads off "i didn't say slap" just tilt the pads with light pressure. But that's for collecting so you can grow it on, if your trying to collect 2 or 3 strawbales worth i'd just stab my pitch fork full and then wipe em off. But I'd never do that.....

Saybian Morgan wrote: I'm not understanding the strategy because I'm having a hard time creating a condition in which I'm in such an abundance of cactus but nothing else that I'd compost

Here prickly pear can cover large areas of overgrazed rangeland, so people try to kill it by poisoning it and sometimes burning it. They also make huge piles of trees such as cedar and burn them, whenever it rains (which is less and less).

Well, it's very invasive over there. It covers some big area's and if you leave one or more segment after cutting it will resprout. So I think it is a good way to make biogas. Imagine something like this on your whole property:

OH man that's fantastic growth, you must have allot of water in comparison to what I'm familiar with. I'd use a pitch fork and just stab and wipe, I'm surprised you can't wood chip it and use it's biological gels as a soil ammendment for water retention.

Well, this is not where I live. I live in the Netherlands (zone 8a, yearround moist). But somebody that I know lives in Turkey and she has a big garden with lots of fruits and vegetables. She's in zone 10b with an annual rainfall of 1000 to 1400 millimeter, but the most of the rain is in winter, autumn and spring. From June to August there are almost no rains at all.

In my experience when a prickly pear cactus pad dries there is very little material left to make biochar from. The pad when dry is almost paper thin, crumbly and still has the small glockets. Most of the weight is water and 'cactus slime'. I have burned (in air) the needles and glockets and they fall apart upon touch.

I am very familiar with opuntia, as I am in zone 11 with less water than her: 400-500mm and nothing from may to october.
They should be greater for biogas than biochar, as they contain a lot of water.

Only old pads will dry providing some dry stuff. It will form some sort of dry grey grid.
It is beautiful and can be used for craft!
It can also be used to start a fire.
BUT the most useful parts, when something dries, goes into the air instead of going into the soil, doesn't it?

Here are some suggestions:
- Cut at the beginning of rain season if you want to make them rot for compost.
- Bury for providing water, eg at the end of the rainy season.
IMO the best use of opuntia.
They will provide water and nutrients for the plants.
- Do not uproot unless you need to clean an area.
They do not grow so fast as big plants, and they will be helpful by providing you with more carbon.
- Let them grow at the boundaries, as a living fence.
- They protect from fires only when they are green. When they get dry and skinny at the end of summer, they can also burn.

About eating and pealing:
You need the technique! Some people collect them with sticks and then cut the 2 ends, and especially the end with the depression full of spines!
Then cut the skin between the 2 ends, pull apart and take out the juicy stuff for eating directly.
You loose the good part close to the skin, the part with no seeds...
But then you can quench you thirst when needed.

When you have time: collect, and gather in a bucket after brushing individually, so that the spines do not pick each other so much. Then at home I put then in a bucket of water. I brush in the water, then quit the 2 ends, split the skin vertically as before.
But I take care to remove only the skin. Watch out for removing well the spots with the spines, as they stick more to the flesh.

Then I mix them all, and pass through a mosquito net to remove the seeds. Very easy and quick to pass it all with the hand. Much faster than the potato masher. And the taste is really better than eating the whole fruit, there is a real difference. It also enhance the slimy part, I guess because it brakes the pectin... Remember that this is medicinal for stomach and guts. I can drink a pint, which I cannot do with any fruit! It never gave me any stomach ache and never found it laxative though I am a sensitive person.

It is one of the best plant to work with in dry areas, do not uproot too much!
I also suggest to chose some cultivars for fruit quality, and also with moderate spines. the young pads can be used in cooking too.

Essentially for making biogas- they are letting material decompose in a low oxygen setting.. which produces more methane. If you are looking to collect and use the methane as another resource while also making compost this is a good concept- but methane is a very potent greenhouse gas when released. In this case.. "juicy" moisture filled plants work great for the digester. If you've ever gone by a landfill and seen a flaming pipe at the top.. this is the same set up in smaller scale- where the methane is instead captured and utilized.

Biochar.. it's char-(coal) produced in an oxygen restricted environment- with variances depending on what they are looking to produce (bio-oil or syngas). Picking a succulent to burn is the worst possible choice as it is comprised mostly of water.

Here's the thing that I get hung up on...
Industries are incinerating biomass materials as a means of disposing of an unwanted or residual byproduct. (Some set ups harness this as an energy source for their production.. waste to energy.) It's done in a controlled setting- so they can vary what they produce and the quality in addition to controlling what is expelled into the environment. They heat it up fast and at high temps to create bio-oil along with biochar. Slowly at lower temps.. and they can create syngas & biochar. The bio-oil and syngas are combustable fuels to feed back into the production system. Biochar.. a byproduct that is now finding an application. The qualities of the char fluctuates according to the process and biomass used.

I'm good with that.. as a use of an industrial waste product.

Just home production just to make char..baffles me. It isn't very eco friendly (producing carbon monoxide, CO2,etc.- and usually wasting the energy- in this case heat.) Typically fails to produce the same quality char... as industrial operations are set up to monitor oxygen levels, capture the gasses released due to incineration, controlled temperatures, etc... and many of the studies touting the qualities.. are from the high temp/fast incinerate method.

*shrug* Just a thought.

Side note.. a problem I had gardening in a semi-arid place (14-18" annually) was not only the soil having high pH.. but as well the city water/ tap water was high (. Even though we made and added mountains of compost.. every time I watered, I sabotaged our progress. (Rainbarrels were illegal there... so I put in a pond and aimed the gutter downspout towards it.) When the pH gets that high.. it starts locking up nutrients in the soil.

Anne, thanks for this, and may be try the opuntia as a source of water at the end of the rain season!

Anne Rambling wrote: Just home production just to make char..baffles me. It isn't very eco friendly (producing carbon monoxide, CO2,etc.- and usually wasting the energy- in this case heat.)

You can avoid wasting it with a TLUD. (Top Lit Up Draft I think)
I would like one for cooking.... and then I put the biochar in the garden! That would be small quantities, as I would not burn more than for cooking, so that I use the energy and do not waste it.

Picking a succulent to burn is the worst possible choice as it is comprised mostly of water.

Though it would be done after drying, yes I see no good use for opuntia there either!