A few years ago, it was explained to us the problem the local community in Tanna had growing vegetables downwind of an active volcano: the volcanic dust smothers the crops, and acid rain burns them. Would a greenhouse solve this? This challenged us to think about greenhouse designs. How could we keep the volcanic dust and acid rain off the crops when the wind blew from the direction of the volcano, but at the same time keep the inside of the greenhouse well ventilated to stop it overheating on calm, sunny days? The structure would also need to withstand cyclone strength winds and earthquakes, and how would we water plants inside a greenhouse? Not easy problems to solve.
A simple gable ended structure proved the most practical design option. Balanced louvres at the ends were devised that would remain open, but automatically close when the wind was from the volcano direction. Walls were earthbags. With the help of friends to engineer and do the drawings, the lengthy process of sourcing and pricing all the materials began. Timber was cut and milled on Tanna. Items sourced in New Zealand were transported, with nuts and bolts throughout the luggage of generous volunteers.
Greenhouse plastic is made from polythene. It contains UV inhibitors to stop sunlight from degrading it quickly. Acid rain does not attack the plastic but it disables the UV inhibitor. After a worldwide search, acid resistant greenhouse plastic was obtained from Bendigo in Victoria and transported to Tanna by a team from Melbourne with their airline luggage. When we got there, we located the site, cleared the scrub, levelled the land, poured a foundation (including anchors for cyclone rods) and over 400 fertilizer bags were filled with soil and pack down firmly. A massive team effort got the roof trusses up. QLD Volunteer builders and their hardworking team who put the roof framing up, were crucial to the work being completed and we thank them for their huge efforts during the build. We extend-ed our stay by a week to try to finish it, but at the end of the extra week we had half the louvres mounted, but still did not have the roof on. It was disappointing to leave it unfinished. Over time, the earthbags that were exposed to the sun were deteriorating. A local builder, was organised to render it with concrete.
Eleven months later, a little older and perhaps wiser, we returned with others to complete the project. After quite a bit of maintenance and three days of calm weather we got the plastic on and fully secured. (see photo). Great jubilation as this was finally achieved!
Locals concrete lined the tanks. Concrete tanks neutralise any acid rain. Students will be able to collect watering can loads of water to use during the dry months.
Whilst there was still work to be done, we headed home exhausted but with glad hearts that it is nearly finished, knowing that the minor jobs left could be completed by locals. Now soil can be prepared and planting can begin! Stay tuned for updates on planting and growth outcomes. May God bless this project.
Tim & Gail, New Zealand