Introduction

Urban agriculture has become a common topic on growing and producing food in a big city. Because of the limitations of the techniques for growing plants or raising animals in the city, it might not be the same methodology as the traditional ways of agricultural practice. Midmore & Jansen (2003) forecasted the challenges and risks for a vegetable farming practice in the peri-urban area of South, Southeast, and East Asia on the basis of the limitations of and the competition for land and labour as resources. Urban agriculture can partly replace the demand for both imports from rural agriculture and the overseas food supply to cities (Mougeot, 2000). City farmers create an environment that can fit their specific needs for urban agricultural activities. The typical typologies of urban farming techniques range from growing plants in soil to soil-less systems in greenhouses or plant factories to outdoor raised bed farming. To create a growing environment in a city where air can be polluted, soil can be contaminated with heavy metal, and water might not be used for agricultural practice, greenhouses provide the opportunity for growing plants under the separated growing conditions. Greenhouses can be used not only to extend the growing season but also to protect plants from diseases and insects. These plastic-covered and netted structures can also control temperatures and allow farmers to design separate irrigation systems for selected plants. However, growing plants under this controlled condition requires both capital for investments and specific knowledge (Bon et al., 2015). Only 67% of the glass/poly greenhouse farms in the USA reported as profitable businesses, while 33% remained unprofitable (Agrilyst, 2017).

Smit and Nasr (1992) emphasised that the geographic location of urban farming still lacks the potential information to develop an urban agriculture database. The critical geography of urban agriculture needs to be analysed before claiming sustainability and health benefits (Tornaghi, 2013). Urban farming should be linked to urban resources through urban planning and industrial ecology. The urban resources can be opportunities for utilising food wastes, wastewater, and waste heat/CO₂ recovery (Mohareb et al., 2017). There are three purposes of urban farming categorised by economic feasibility as follows: 1) public urban farms, 2) non-profit urban farms, and 3) commercial urban farms (Phillips, 2013). In the Asian context, particularly in Tokyo, Shanghai, and Singapore, there is interest and demand in greenhouse farming and controlled environment agriculture (Benke & Tomkins, 2017). In Bangkok, according to a Thai city farm map, there are 19 locations of urban farms and learning centres within the inner ring road (Kanchanapisek Highway) on the website (accessed 19 October 2020). There are 11 locations of urban farms including rooftop farming, school yards, therapeutic urban farms, household farming, community gardens, and institutional farming. The other type of urban farming also provides a learning facility and training programs for specific groups of learners. There are eight locations of learning centres, including learning centres for children, vertical farming, rooftop farming, sustainable household, and on-ground urban farming. On the basis of the survey of Urankul and Jiraprasertkun (2016) combined with the data from Bangkok Metropolitan Administration surveying on increasing the green space, 15 locations of green roof agriculture on the rooftop of government agency buildings were reported. Suteethorn (2011) defined Bangkok’s urban farm patterns as three characteristics as follows: 1) existing vegetable gardens in the city, 2) urban fringe productive landscape, and 3) urban farm rooftop vegetable gardens. Boossabong (2018) focused on specific case studies on the collective community based urban farming. The urban farmers of the west side of Bangkok used learning centres as a platform to share the urban agricultural network and knowledge as well as the way to negotiate with the local government. Urban farmers work as not only producers but also sellers at the same time (Montrivade, 2014). Furthermore, the typology of urban farming could be divided by farming purpose, scale driven, locations, and farming techniques.

Based on the literature reviews, there is still a gap on understanding the landscape patterns of such complexity systems of urban farming, particularly toward the business opportunity and greenhouse farming in the urban area of Bangkok and its surroundings. From questioning the linkage between local food and the behaviour of multiple actors on food production and consumption in the Bangkok Metropolitan Region, we need to understand the ecosystem of peri-urban food based on the geographical approach (Tsuchiya et al., 2015).

This paper highlights the missing layers of urban farm locations and is focused on the commercial perspective of producing crops in the city of Bangkok and its surrounding provinces. As there is no database on urban agriculture locations in Bangkok Metro Region (BMR), the current data do not cover the existing urban agriculture. This paper focuses on reviewing and analysing greenhouse urban farm opportunities and challenges.

Literature review

Because of the limited resources and pollution in the cities, urban farming faces challenges related to resource scarcity, including water, land, labour, accessibility, and environmental contamination. Bon et al. (2015) mentioned that usually, urban horticulture practitioners are obliged to rent from the land owners or to farm on public land as there is high land pressure on the urban property and such property is expensive.

Greenhouse urban farms can be defined as ground-based-conditioned, and a traditional greenhouse attached on the rooftop could be considered to an integrated-condition building (Goldstein et al., 2016). Growing plants in a greenhouse tends to have a very low net water consumption but very high energy input per kilogram of crop production (O’Sullivan et al., 2019). The research on the energy conservation of greenhouses refers to guidelines including either energy saving with electric motors or with electric motor control systems and energy management in closed-system greenhouses (Namhormchan & Mueangchan, 2020). The study on green material explores the potential for the manufacturing process to develop natural fibre-based materials for urban farming. These biocomposite materials can be used for supporting climbing plants by using hydrophobic green materials (Baharudin et al., 2018). Heavy metal and air pollution can be a concerning limitation for urban farming that can lead to crop toxicity. Bon et al. (2015) stated that some species such as pea, bean, pepper, tomato, and melon have the ability to slowly uptake heavy metals.

In 2018, Thailand had a total of 1,498 rais (239.68 ha) of melon farming land, which produced 4,837 tons of fresh melon. The average productivity was 4,421 kg/rai or 2.8 kg/m2. The top growing area was in Supan Buri, Sara Buri, Ayutthaya, Kanchana Buri, and Buriram (Department of Agriculture Extension, 2019). Bangkok and the surrounding areas were not listed as melon farms in this case. It seems that Bangkok and the surrounding metropolitan areas which have a local registered population of 16 million people (National Statistical Office of Thailand, 2017) cannot produce this type of fruit, which can be bought in almost every supermarket. This could be the argument for this research to look closer into the local urban farm networks which aim to produce and serve fresh fruit and vegetables to the local community within the Bangkok Metropolitan Region, by studying the location of greenhouse urban farming and understanding this farming activity from the perspectives of the opportunities and constraints of city farming.

Objective and methodology

There are two objectives of this study to understand landscape patterns and analyse the challenges and opportunities of greenhouse urban farming within BMR:

1. Understand the landscape pattern of greenhouse farming within BMR.
2. Analyse the challenges and opportunities of greenhouse urban farming in BMR.

The study included surveys on the greenhouse locations and focused on in-depth interviews with the farm owners who were willing to provide the information and discuss the challenges and opportunities of doing agribusiness in the city and on its periphery. The study areas included Bangkok and the five surrounding provinces of Bangkok, namely Samut Sakorn, Nakorn Pathom, Nonthaburi, Pathum Thani, and Samut Prakan, which are called Bangkok Metropolitan Region (BMR).

The advantage of the in-depth interview method was the ability to capture insightful lessons learned from the greenhouse urban farming practices, particularly from farmers who wanted to share their expertise. Moreover, this method allowed the research team to observe the greenhouse urban farming activity and management systems in detail. The disadvantage of choosing this method was that it was limited when we excluded the greenhouse locations that chose not to share their points of view on farming in the city.

Results and discussion

The survey on greenhouse farming within BMR was conducted from August to October 2020. The results illustrated the greenhouse urban farming locations, operations, management, and marketing tools within BMR.

Figure 1 shows the greenhouse farming locations (green pins) and the focus-group greenhouse farming locations (dark green pins with circles). The results showed that there were 57 urban greenhouse farms located within Bangkok, Samut Sakorn, Nakhon Pathom, Nonthaburi, Pathum Thani, and Samut Prakan. By simply asking all of the urban greenhouse farms to provide an inside interview, I found that 20 farmers wanted to share their backgrounds and knowledge on greenhouse urban farming techniques as well as their views on the opportunities and challenges of investing in greenhouse businesses based on their models and locations. With respect to the locations, I found that 11 urban greenhouse farms were located within the ring road and were mixed with the built-up area. While the other nine greenhouse urban farms were situated outside the ring road, where the adjacent land might still open up as the agricultural landscape.

Table 1 shows the background information, programming, and locations of the focus-group greenhouse urban farms. For the example of 20 greenhouse urban farms, this table illustrates that 60% of the interviewed farms had cafe space to serve the surrounding communities and visitors, 30% of the farms owned restaurants that directly served fresh produce from their farms, 20% of the farms offered short courses and training programmes at their learning centres, and 25% of the farms invested in other agribusiness, such as poultry farms (15%) and orchid farms (10%).

Table 2 illustrates the land, water, and greenhouse operations as well as the opportunities and constraints reflecting on the management techniques. On the basis of the focused group survey, this table captures the resources availability and operation techniques which can lead to the choice and decision making on greenhouse farming management. This part can be divided into four issues: land ownerships, water resources, greenhouse materials, and operation costs.

Greenhouse designs and systems

Figure 2 shows the greenhouse typology on designs and systems including greenhouse structures, type of growing technique in greenhouses, water management, and plant selection.

There are four types of greenhouse designs with respect to the different forms of structures: sawtooth greenhouse, gable roof greenhouse, skillion greenhouse, and shade greenhouse. Most of the urban farmers chose and invested in a greenhouse with an arched roof called a skillion greenhouse. This might be the simplest form to build and the cheapest one as compared to the other forms of greenhouse structures. However, the temperature inside this roof structure is quite warm as compared to that in the sawtooth greenhouse, which was also found from this survey. As sawtooth structures allow the air to circulate inside the greenhouse better than the other roof systems, the temperature inside this type of greenhouse is usually similar to the outdoor temperature. A gable roof and shade greenhouse was also found but was not as popular as the other two types of roof designs.

With respect to the growing techniques, there were four types of practices used inside the surveyed greenhouses. The first typology was raised bed planters. The material used for the curve was concrete or bricks. There was no wastage of the containing material in greenhouse growing plants with this technique. The second type of growing pattern inside of the greenhouse was container or pot plants. The common material used in this case was PE bags or plastic pots. The farmers needed to replace the PE bags after using them three times. The upgraded material of the PE bags was plastic pots, which could be used for a longer period of time. Ridge and furrow farming were also used in the greenhouses, particularly on the outer edge of the city where the development was not dense. This was the growing technique closest to the traditional method of farming. The additional part of the traditional technique was the PE sheet used to cover the soil. In this new technique, this growing system also produced some agricultural waste, such as the plastic sheet.

As mentioned already about the water resources which could have different sources, the farmers also controlled the irrigation system differently according to the needs of the plants and the plant species. For example, in the melon cultivation techniques, they relied on two types of watering systems, namely drip and fog irrigation.

With respect to the plant selection, the common plants grown in the greenhouses in BMR were Cucumis melo L. var. reticulata, Cucumis melo var. Cantalupensis, Citrullus lanatus, Lycopersicon esculentum Mill., Cucurbita moschata, and Ficus carica. Most of the urban farms promoted a variety of melon cultivars as the main products growing in greenhouses. Usually, the cycle of the planting to the harvesting of melons is approximately 120 days; this allows urban farmers to grow 3–4 crops per year within a controlled environment.

Table 3 shows the greenhouse management and the plant selection from the focus-group survey.

According to the observations, the greenhouses in BMR mostly produce exotic plants and herbs, including melon, butternut squash, tomato, and hops. The common species that this study found are the melon planted inside the greenhouses. However, there is an argument on the method of planting melons in an open field without a greenhouse structure in the city. From the author’s perspective, urban farmers can manage to carry out this agricultural practice as long as they have sufficient space for the planting experiments. In the case that the land is quite small or limited, most of the farmers choose to grow melon in greenhouse structures for maximising space, extending the growing season, and protecting the plants from disease.

Marketing analysis

Online social media brings an opportunity to the urban farmers to promote their fresh urban produce, products, atmosphere, and farming activities. By doing so, urban farms can connect and reach out to the customers who are interested in Facebook pages and can reach a wider range of customers. Moreover, supporting programmes such as cafe, restaurant, and/or learning centre can be an attraction to bring more people to the farms.

Furthermore, urban farms can gain benefits from the low cost of promotion on social media; they can use the traditional media such as newspaper and television channels for writing and filming their urban farm stories. For doing so, most urban farmers have multiple channels and ways to promote their urban farming and greenhouse businesses at a low cost. Most of the farms interviewed were in the early stage of farming in the city, not more than 10 years, and social media had a positive impact on promoting these urban farm businesses directly. Urban farmers can also set up their own price, which is higher than the standard market price. I found that the most expensive fresh melon produce can be higher than the market price by seven times. Usually, most of the urban farms sell the fresh melon from their farms for three times higher than the market price. Selling without the involvement of the market middlemen can be one of the incentives for producing urban fruits and vegetables.

The other activities on urban farms such as cafes and restaurants also act as a magnet to draw the local neighbours and customers from the city to the urban farms. More than 50% of the surveyed farms provided these facilities as tourist attractions. These could be one of the tools for developing the business branding and image. I found that a few urban farm places reserved the freshly produced fruit only for serving as food and beverage in their own cafes and restaurants. This is one way in which urban farmers can earn more than selling the whole fresh fruits. Promoting these urban farms through social media can lead to attracting the online media and traditional television channels to the urban farm locations for urban lifestyle pieces.

The main products including melon, salad greens, tomato, and other types of vegetables are either sold in place or processed into food and beverage served in the cafes or restaurants. The survey found that 55% of the local farmers sold both fresh melon and a melon-processed dish or drink, 40% of the farmers sold only fresh fruits, and only 5% of the local farmers sold only the food processed from the melon grown at their farm. For example, fresh melon can be sold at the urban farms at prices ranging from 100 Baht/kg to 350 Baht/kg, which is about two to seven times more than the standard price. Most of the urban farms sell their fresh melon at 150 Baht/kg, which means around three times higher than the standard market price. In one of the deep interviews with a local urban farmer in Klong Sam, Pathum Thani, I found that the owners set the price to sell fresh melon, salad greens, and sunflower sprouts at the same price of 250 Baht/kg. This price is higher than the market price by about five times for melon, two times for salad green, and two and a half times for sunflower sprouts. The owner said that the price could be set higher than that of the products sold in the hyper market or wholesale market, as the customer could learn about the process of growing fruit locally. Moreover, this urban farm location was close to one of the wholesale markets situated on the north of Bangkok, called Talaad Thai.

With respect to the processed-food dishes and drinks, it can be creative and a value-add for attracting the customers to the farms. The most common menus in the local restaurants and farm cafes include melon ice cream, detox drink, melon salad, melon cakes and tarts, freeze-dried melon, and melon curry. The price can be set higher depending on the quality and presentation of the dishes or drinks. The local urban farms plan to sell these products according to the demand of the customers to match with the supply from their farms and networks.

It is clear that while the local farms cannot meet all the demands of the green consumers around Bangkok, the local urban farmers can establish local customer relationships, produce urban food, and set reasonable and sellable prices, which are still higher than the standard market prices. Furthermore, one of the tools that can be used to promote urban farms matches the social media applications which provide the ability to draw customers to the hidden urban farm locations in the city.

Summary and Findings

Greenhouse urban farming creates a closed loop for self-sustaining growing business models, producing fresh fruit and vegetables, and functions as a distributing node for the surrounding communities. This controlled environment of growing plants fits with the concept of urban farming, as it can either require a land-based property or be installed on top of a building. Most of the surveyed greenhouses in BMR are land-based system. Few of urban farms explained their plans to upgrade and extend rooftop greenhouses. Rooftop greenhouses can be based on a technique called ‘Zero-Acreage Farming’ (ZFarming), which depends on the non-use of land for farming practices (Thomaier et al., 2014). However, both urban farming and new ZFarming practices can be as unsustainable as regular farming if not managed properly (Specht, 2014). This concept can be used for the new learning opportunities for both urban farming practices and customer experiences.

Most of the greenhouse businesses in BMR are run as family businesses. Furthermore, 80% of the survey group owned the land, and 20% still rented the land for the greenhouse and agribusinesses. I found that few of the business models which still rented the land planned to buy the property because of the profits that they could make from the urban agriculture business.

With respect to the typologies of practicing greenhouse farming in urban areas around Bangkok, I found that there are many ways of designing the structures, choosing the types of growing techniques, water management, and plant selection. Thus, greenhouse farming in the city is quite complex with respect to planning a systematic design as well as the management systems. The cost of designing greenhouses could range from $25 to $150 per square metre depending on the material, system, and technology used. The cost of the greenhouse structures can reflect the technological level of the controlled environment structure, which ranges from low to medium to high technology (Ponce et al., 2014). According to the survey, most of the urban farm greenhouse structures within BMR are still considered to be low to medium technology. However, some of the urban farms have started to invest more on the use of high-technology equipment in their existing greenhouses; the cost of smart technology is relatively high. Most of the greenhouse farming requires a set of knowledge and understanding of the tips and techniques as well as a reasonable investment budget, for investing in the development of a control environment which is suitable for growing exotic species. Thus, most of the urban farmers in the interview process shared their common background on engineering and marketing.

This reflected that the management of greenhouse urban farming is quite complex and that urban farmers need to have appropriate knowledge and skill management. The opportunity to share this knowledge is also important in terms of both earning more profit on urban farming and expanding the local networks within the different locations. Urban farms with multiple programs can position their businesses as an agritourism destination in the city fabric. The question remains now is whether in terms of the diversity of urban farming, digital urban farming or large-scale indoor plant factories can replace this wide range of complexities (Carolan, 2020).

This study could be used as a database for researchers, urban farmers, and the locals who want to jump into this business. The future research related to urban farming and greenhouse design should focus on these other areas including: 1) land organisation and development, 2) material and cost management, 3) growing and post-harvesting strategy, 4) marketing and branding, and 5) smart farming and technology management.