Hi Mengyao / SSTC,
Thanks for your questions and I apologise about our delayed reply. It’s great that you are considering local, sustainable materials for greywater treatment.
For coconut shells, we didn’t see many trees when we visited but from researching online we are aware there are coconut trees in Far North Queensland and Cape York Peninsula along the beaches: http://www.pacsoa.org.au/palms/Cocos/nucifera_oz.html
However you will need to do further research online on how many there are, or make an assumption about how many there are. This FAQs document will help you make assumptions and state them in your report where you cannot find exact data.
If it is a relatively small number of coconuts you need (less than a couple of hundred) then you could assume you are able to collect them your own or employ someone who is skilled to do so, as I found others do this already: https://www.abc.net.au/news/2017-09-30/should-we-be-doing-more-with-australian-coconuts/9000884
However I recommend you check local laws online if this is forbidden. If you need more, you may need a license to collect them or need to import them from overseas and purchase them in larger quantities. You should be able to research the retail price, or assume a discount if bought in bulk.
For sand, from my quick Google search it seems collecting sand from beaches is illegal in large quantities as it is considered ‘mining’ which requires permits. I’m not sure about limits – you should be able to research online any laws around this if there is any, but there might not. It can also be damaging environmentally to ecosystems to remove sand, so keep this in mind if you need large quantities. However if it is a small amount, like a few buckets full, this might be okay. Assume the beaches contains some shells but not much debris apart from some seaweed in some areas.
In terms of where people live, you can use Google maps and zoom in (if you can access it) to see where towns are along Cape York Peninsula to see where most people live in relation to the beach. There are some coastal towns beside the beach, however the focus of this year’s EWB Challenge are remote outstations and homelands – so mostly inland communities or homesteads several hours from the beach. There is also sand inland of different soil types so consider whether this is also suitable.
I hope this helps. After you’ve done some more desktop research online, let us know if you have any further questions.
Best of luck,