Is vertical farming a more sustainable alternative to conventional farming in Hong Kong?

Abstract

Hong Kong’s agricultural sector has been declining since the 1980s with the reduction in area of arable lands and number of farmers. The trend of over-reliance on imported produce is likely to continue with population growth in the upcoming decades. The climbing imported to locally grown food ratio might aggravate climate change. Vertical farming, which is promoted in recent years as a more sustainable mode of farming than conventional cultivation, is investigated mainly in terms of life cycle Greenhouse gases (GHG) emissions of its produce.

Assessment was carried out following the guidelines in two relevant sets of Publicly Available Specification (PAS). Lettuce variety “Heading European”, which is among the most popular leafy vegetables in Hong Kong, is chosen because of its significant share imported from Guangdong Province. Three sets of surveys have been conducted to find out if locally grown produce generates less GHG than imported one. The sustainability of vertical farming is also evaluated. It performs in a cradle-to-gate basis in which life cycle of the lettuce is assessed from the stage of farmland preparation to delivery of them to Vegetable Marketing Organization (VMO).

The results of life cycle GHG evaluation show that produce of local farm generates fewer amounts of GHGs than the imported one. For lettuces imported from the conventional farm in Songyuancun, Guangdong Province, it generates approximately 1.57E+00kg of carbon dioxide equivalent (CO2-e). It is about 132% higher than the one grown in local conventional farm at Tai Kong Po Tsuen, which is around 6.77E-01kg of CO2-e

It seems the idea of replacing local conventional farming with vertical farming is not sustainable at this stage. Evaluation reveals the latter generates more amount of GHG which is 8.72E+00kg CO2-e/cup of Oak Leaf Lettuce. It is about 13 times higher than the locally grown in the conventional farm.

The energy-hungry lighting system and the lack of renewable energy are among the major reasons for high GHG emission in vertical farming. Although the GHG emissions are higher than conventional farming in the designated lifecycle, vertical farming does contribute to sustainable development in terms of food stability and job opportunity.

Uncertainties of this study could well be improved by developing a specific set of GHG emission factors for components in preparation stage and on-farm stage. More information could be collected for use and end-of-life stages, which is omitted in the study. Further comparison of wider variety of vegetables cultivated in different forms of farming should also be carried out. Carbon labelling scheme for agricultural products would brush up environmental awareness of both producers and consumers. With the trend of green consumption, it would provide an incentive for producers to adopt this scheme. It is especially important for local vertical farms to impose this scheme to increase its market competiveness.

Moreover, government should play a significant role in promoting a more sustainable form of agriculture. Supportive policy like increasing investment in R&D for energy efficient technologies or even erecting a modern building for vertical farms would help achieve this goal. The lowered life cycle GHG emission would enhance sustainability of vertical farming.