What is a polytunnel in coffee drying?

A polytunnel in coffee production is a greenhouse-like structure made from metal hoops covered in translucent plastic sheeting, used to protect drying coffee from rain, excessive sun, and temperature fluctuations. It's increasingly used alongside or instead of open raised beds, particularly in regions with unpredictable rainfall.

By controlling the drying environment - maintaining airflow while excluding rain - polytunnels allow producers to dry more slowly and evenly than open-air conditions allow in wet weather, and to continue drying during rainy periods without compromising the lot. Temperature inside can be moderated by opening vents or sides to prevent overheating.

The controlled environment is particularly useful for experimental processing methods where drying conditions are a critical quality variable. A long-fermentation anaerobic lot that dries unevenly due to unexpected rain loses a lot of the careful work done in the fermentation tank - a polytunnel protects that investment.