As you may have gathered, the plastic bottle photobioreactor project is a new idea that is intended to repurpose as many intact plastic bottles as possible, to grow microalgae.
Between 8 and 12 million metric tonnes of plastic ends up in our oceans each year. Over 80% of it coming from land-based sources [1]. Low & Middle-Income countries do not have established recycling facilities, so this contributes to plastic ending up in landfill, being incinerated or littered. It gets carried by the weather into rivers and out to sea.
Over the past years, demand for plastic has substantially increased in sub-Saharan Africa and is projected to follow the same trajectory over the next decades — one estimate indicates a growth of 375 percent in sub-Saharan African and the Middle East and North Africa combined, compared to a global average of 210 percent by 2060 [2].
Fortunately, many of these countries are also in global regions that have ideal conditions for growing microalgae. So, if a localised use for the plastic waste can found then it’s suddenly no longer waste. It has an increased value. It’s shifted from Linear usage to Circular usage.
The concept is to sort bottles into intact and damaged collections. Intact bottles (grouped into the same size & shape) can be mounted in parallel onto a manifold array, so microalgae can circulate in and out of the bottles. Damaged bottles can be recycled into ‘flake’ and moulded into the assembly parts.
‘Mark 1’ bench assembly investigations looking into different mounting methods.
‘Mark 2’ early stage horizontal manifold development using off-the-shelf parts to assemble 2 banks of bottles 2×12 Coca-cola bottles ( 2 x 2 x 12 x 1.75 litres = 84 lites capacity)
‘Mark 3’ vertical development mock-up of a modular unit with stands capable of holding over 80 bottles each. This gives an areal growing volume of over 900 litres/m2. These can be packaged inside a standard 40-foot container with temperature, CO2, nutrients & light control, providing about 27,000 litres of growing capacity.
We are continuing with developments to improve the design for injection moulding, CO2 recovery, O2 removal, biofilm prevention & cleaning.
| Ref. | Source/Attribute | |
| [1] | https://www.refill.org.uk/the-problem-with-plastic-3/ | |
| [2] | https://www.greenbiz.com/article/heres-why-human-centered-design-required-marine-plastic-innovation | |