By Trevor Richards, SE Asia Biochar Interest Group; all photos courtesy of the author
Although the term biochar is relatively new, charcoal has been added to soils for millennia through natural processes (forest and grass fires) and by human hand. There is a long history of charcoal addition to soils by humans throughout the world—this story highlights the modern use of biochar in Malaysia (known as tanah hitam).
Bandar Utama is a small suburb located about 15km to the west of central Kuala Lumpur. Until 1991, the land now known as Bandar Utama consisted of plantation estates with fewer than 100 people living in the area. In the early 1990s, development began under the See Hoy Chan Holdings Group and today, Bandar Utama is a vibrant, rapidly growing township with a population of about 200,000. A focal point in Bandar Utama is the 1 Utama shopping complex which opened in 1995 and has nearly 500,000 m2 floor space. It also boasts its own ‘rainforest’ that grows up through all six levels at the SE corner of the shopping complex, and has the largest rooftop garden in South East Asia, known as ‘The Secret Garden’.
Experimentation with biochar in Bandar Utama began in a small forest nursery in 2002 following the engagement of Dr Francis Ng as a consultant in 2000. Dr Ng is a botanist based in Malaysia, after a career with the Forest Research Institute of Malaysia (FRIM). While working in Bandar Utama, Dr Ng started collaborating with Alfred Cheong, the Landscape Manager for Bandar Utama’s development projects. Dr Ng worked on establishing the 1 Utama ‘rainforest’ and utilized biochar in the soil mix for the 50 species of trees and plants within the rainforest development. He explains… “Needing a large volume of good soil to establish a rain forest in the ‘1 Utama’ shopping mall in Kuala Lumpur, I decided to make such a soil by mixing charcoal particles with soil. We made this soil by mixing normal clayey soil (mostly subsoil) with charcoal and coconut fiber in equal proportions by volume. The charcoal was conventional charcoal produced by the kilning of mangrove wood. This came in large hard pieces that had to be broken up mechanically. The resulting particles were irregular in size and difficult to mix with the clay and fiber. I then found a much better source of charcoal in the factory of a charcoal briquette manufacturer. Charcoal briquettes are made by compressing sawdust into standard-size briquettes for kilning. The briquettes, meant for the barbecue market, can be easily broken into particles, sieved to remove dust and graded into the desired sizes. We refer to the product as horticultural carbon (Ng, 2006). We use two sizes: 1 – 4 mm particles for potting mixtures and 5 – 12 mm for garden beds.”
Of particular interest to the biochar research community around the world has been the successful use of very large quantities of biochar in the garden. Over 800 m3 of soil was required for the garden with an average depth of 300mm. The average volumetric application rate of biochar was about 50%, many times the current utilized practice for biochar soil mixes. Says Dr Ng, “An explanation of why I used charcoal needs to be given within the context of Malaysian soil properties. Because of the year round high tropical temperature, high rainfall and lack of volcanic activity our soils are ancient and highly leached. In the original forest soils, the organic matter is a very thin layer on the top of what is almost pure clay. The soil that is available for gardening is almost pure clay because the organic matter is lost soon after the elimination of the original forest. The problem with clay is that it gets compacted easily and retards the movement of water through it. For most agricultural and horticultural plants, the soil has to be regularly tilled to break up the clay otherwise root growth is retarded due to lack of oxygen.
Plants can be grown in pure water, as in hydroponics, provided the water is continuously aerated, In soil, the roots get oxygen from fresh water supplies. Soil has to be free-draining so that fresh water containing dissolved oxygen is continually available to flush out stagnant deoxygenated water. Organic matter such as humus incorporated in soil helps to prevent the clay particles from clumping together but in the humid tropics, organic matter is decomposed within one year. I needed something long-lasting, yet natural and able to hold nutrients, Charcoal was the best option. On the rooftop, charcoal has the added advantage that it is half the weight of soil of equivalent volume.”
Following the success of using biochar in the modified soil applications at 1 Utama shopping center, Dr Ng and Mr Cheong began experimenting with its use in the many urban landscaping projects that Mr Cheong was managing. With Bandar Utama undergoing rapid development, many new housing projects and public buildings require landscaping. Biochar is being used in the private and shared space gardens and lawns and has been incorporated in the local golf course clubhouse development.
Mr Cheong, a landscape architect trained in New Zealand, had experience with commercial urban landscaping methods in Kuala Lumpur which typically involve the removal of construction debris and contaminated soil followed by application of imported commercial top soil. Commercially available urban top soils in Malaysia, Singapore, and other tropical countries often have very high clay content and low organic matter with little nutrients. Even with the nutrient deficits, importing this soil into the city is expensive, as is the disposal of the contaminated soil it replaces. Often, turf is installed on the imported soil for an instant green look, but the turf often fails to thrive. The biochar system that has replaced this system requires only the raking out of larger construction debris followed by a 15 – 25mm layer of biochar which is rototilled to about 100mm. Dr Ng comments… “For the lawns in the new housing developments, biochar is tilled into the ground to make up for the volume of rocks, bricks and other debris taken out. The lawn grass planted on top is thereby seated on a layer of porous soil (and biochar) instead of compacted clay. Obtaining soil for the garden has become a problem in KL because it has to be trucked in from far away and the quality is poor and inconsistent. Biochar is initially sterile and consistent – the results have been visibly superior.”
For trees and shrubs, the soil that is excavated for planting is mixed at a ratio of ~30% biochar before being replaced with the planting. The nursery root-ball is left undisturbed. Since 2008, landscaping work in Bandar Utama has incorporated about 1,000m3 of biochar—covering approximately 2 – 4 hectares. The total quantity of biochar purchased to date is over 1,100T or about 2,200m3.
The application of biochar in the landscaping work at Bandar Utama has grown organically from practical experience gathered over the last 12 years. It has not been driven solely by economics but this is an important factor in its continued use. Landscaping with biochar has provided a 75% to 90% reduction in soil procurement, transport and handling and similar reductions in waste and debris handling and disposal. Time and labor cost savings can be substantial as the removal of debris and replacement with topsoil is often by manual means with restricted access. Other economic and environmental benefits can be considered including reduced maintenance costs associated with the improved performance of the grass and reduced material transport.
Ongoing and future applications
The development of Bandar Utama is a long term process and its future urban landscape work will continue to incorporate biochar. For example, the Bandar Utama 9-hole golf course is applying biochar into the landscaping of the clubrooms and is considering including it in the course management regime.
The Bandar Utama office tower, 1 First Avenue, was completed in 2010 and has been awarded the Malaysian Green Building Index Gold Standard. Biochar was used in the green areas, and the tower may be the first in the world to incorporate a turfed helipad with 50% biochar mix. Other green building projects incorporating biochar are in the planning stages.
Biochar production plans from urban green waste
The product currently being used as biochar is a byproduct from the charcoal briquette industry originating from timber sawmills in Malaysia. Extruded briquettes are fired in large batch kilns throughout Malaysia and marketed to Japanese and Korean restaurants and the urban BBQ market. The product must conform to quality standards to achieve premium prices. These quality standards lead to production methods that ensure sustained high temperature, high carbon, and low volatiles. This offers some certainty on the quality of the charcoal being used as a biochar. A significant proportion of the briquette production does not survive the aesthetic quality control standards so can be diverted to other uses, but the availability and cost of this material is vulnerable to competing uses.
Bandar Utama has a steady supply of urban green waste and woody biomass from tree maintenance work. Mr Cheong and his team have begun exploring options for local biochar production by fabricating two TPI kilns and are now conducting training and trials. They identified a production site within Bandar Utama, but because these kilns can be smoky on start up, it remains to be seen if they can be operated successfully in this semi-urban environment. The kilns were chosen to accommodate the steady supply of larger tree limbs, but other processing options may be considered in the future.
Summary and vision for the future
The ongoing work with soil carbon in Bandar Utama has evolved from the knowledge and practical experience of Dr Ng and Mr Cheong over the last 12 years. This work has grown in parallel to, but mainly in isolation of, the international biochar movement. With more information reported on the biochar/soil mix at the Secret Garden, the international community is taking note of this work including the successful creation of a lightweight soil media for green roof development; the proven economic and environmental benefits for turf grass application; and the improved urban tree growth, health, and survival rates.
Performance monitoring and records have not been kept so any statements about the success of this work are anecdotal. But the ongoing commitment to its current utility and future production plans are evidence for biochar efficacy in this urban environment. There is a great opportunity for the science community and landscape industry to come together in the future to study the performance of biochar in these commercial and practical application settings.
Bandar Utama, Malaysia (all photos courtesy of the author).
Dr Ng and Mr Cheong
Cassava crop from a single cutting grown in pure biochar after about four months on the rooftop garden of 1Utama.