Solar charcoal, cashew nuts process and new evolutions

Posted 20 May 2019 by Lorin Symington.

Prototyping: beautiful (sometimes frustrating) and creative (sometimes repetitive trial and error iteration) prototyping! Building innovative new solutions to problems presented to us by our partner and their stakeholders on the ground.

We’re in a very interesting phase here on the outskirts of Cagayan de Oro in Mindanao, Philippines. We’ve built two hybrid oven/roasters, very similar to those we’ve deployed in Kenya, though with a few notable improvements to stability and durability around the light window and the door.

We’re currently developing two new applications for making charcoal and removing Cashew Nut Shell Liquid (CNSL). Below, a series of pictures showing various rough prototypes, stakeholder context and some fun around the workshop. Enjoy.

Coconuts:

Tropical paradise that it is, The Philippines has an abundance of coconuts. The hard shell of the coconut is on par with many hardwoods in terms of energy density and it is often converted into charcoal by burning it in an oxygen deprived environment (pyrolysis).

Above, an ‘improved’ steel drum charcoal kiln. Improved is a relative term… this is more efficient than building a great big fire and then dousing it with water or smothering it with dirt or sand, as is done in many places around the world. How would you like a smoky charcoal business in your neighbourhood? My initial calculations indicate 6kg of coconut shell makes 1kg of coconut shell charcoal, which is in line with UN averages for cottage industry charcoal making.

Some of the team during the second test of our coconut charcoal maker, after we tested it without insulation to get a baseline. This application is particularly exciting for me because this is a way to displace a huge amount of dirty emissions and increase the earning potential for coconut farmers. No longer will they burn up most of their coconut shells to get bit of charcoal. This application might triple the income from coconut shell byproducts for small farmers.

A very successful test run. 90% of the coconut shells were converted to charcoal, with only the shells at the bottom of the drum remaining uncarbonized. We’ll solve that by diverting the flammable gas that emerges from the chimney to the bottom of the drum.

A surprisingly sharp dividing line between converted and unconverted charcoal.

Cashews:

The Philippines is one of the major cashew producers in the world, especially considering the size of the country. If you’ve ever wondered why cashews are so expensive it is because they are a very weird nut whose processing must be very careful. The cashew nut grows on the bottom of the fruit of the cashew tree. Inside the shell, between the outer shell and the edible kernel on the inside is a dense spongy pith, filled with a remarkable cashew nut shell liquid (CNSL). The liquid is highly acidic, flammable and quite toxic!

It is a raw material of multiple uses in developing drugs, antioxidants, fungicides, and biomaterials. It is used in tropical folk medicine and for antitermite treatment of timber. CNSL may be used as a resin for carbon composite products and as petrochemical substitute, etc. Wikipedia
As such, CNSL has a value on par with refined petroleum products, making it a potentially interesting source of income.

Traditional cottage industry processing involves heating the cashew nuts in a perforated pan on an open flame. Once they are sufficiently heated, they burst, and the CNSL spews forth and everything catches fire. They’re removed from the fire, dumped on the ground and doused with collected rainwater.

Cashew processing is a family affair. Once the cashews are cooled, the women crack them open and extract the kernel. The shells and the fluid are all the fuel the fire needs to burn and smoke like crazy all day long. The smoke is acrid and heavy and wafts across the neighbourhood, to the detriment of the health of all involved.

First prototype… steel mesh on square tube - aka what happens when you stick the nuts in the focal point? They burst! There’s no fire. There’s less smoke. However, you need to stand in the sun constantly waving this contraption. Also, the focal point is so hot that the CNSL on side facing the sun bursts out, but on the sides the liquid remains (think about how much solar energy you get at sunset versus noon).

It might not be ideal for CNSL removal but it makes a great fish frier!

How to get even roasting? Build a steel mesh drum, put it in a box with a window and fire away! However, the bursting of the liquid from the shell coats the glass, which is not sustainable.

We’ve made a few more prototypes and we’re zeroing in on a good design… a design where we’ll replace young Jerson here with a solar panel and a motor.

The new faces you see are some of the students from the University of Technology of Southern Philippines (USTP) who are doing their summer internship with us, some of whom will continue on to quantify certain aspects of GoSol’s solar tech and assist with data collection and validation of results reported by CarbonCycle and the end users.

Initial tests on the rooftop of the library on USTP’s Cagayan de Oro campus.

The great news is that the ladies and gentlemen from the cashew cooperative we’re dealing with say that the nuts are of a high quality, that the liquid doesn’t get forced deeper into the nut and contaminate the kernel, which often happens with the open fire frying method, meaning they must sell those nuts at a discount. They’re excited to receive training on the SOL5 and integrate it to their production.

Stay tuned, because that’s the next phase of the project!


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