To be presented at the Second International Vetiver Conference -- Thailand, January 2000

THE GLOBAL IMPACT OF VETIVER GRASS TECHNOLOGY

ON THE ENVIRONMENT

Dr. Paul Truong

Resource Sciences Centre

Queensland Department of Natural Resources

Brisbane, Australia.

1. Introduction

The Vetiver Grass Technology (VGT), which is based on the application of vetiver grass (Vetiveria zizanioides), was first developed by the World Bank for soil and water conservation in India in the 1980s. In addition to its very important application in agricultural lands, scientific research conducted in the last 10 years has clearly demonstrated that VGT is also one of the most effective and low cost natural methods of environmental protection. As a result VGT is now increasingly being used worldwide for this purpose. For this reason, vetiver grass is known as a wonder grass, a miracle grass and a magic grass in various parts of the world

The two main factors that contributed to the global application and acceptance of VGT are, firstly, the availability of scientific data to back up anecdotal field observation and also to provide explanations to vetiver’s phenomenal and unique characteristics, and secondly, its promotion through The Vetiver Network by Dick Grimshaw.

In term of scientific research, the two most significant breakthroughs are, firstly research leading to the establishment of benchmark tolerance levels of vetiver grass to adverse soil conditions and heavy metal toxicities in the last six years and more recently on bioremedial measures which had direct applications in environmental protection. The second breakthrough is research that established the structural and shear strength of vetiver roots. Although this is not directly related to environmental protection per se, it gave engineers more confidence in specifying vetiver for steep slope stabilisation, which in turn protects infrastructure from erosion.

This paper presents the state of knowledge of the proven and potential applications of VGT in the field of environmental protection including the protection of terrestrial, aquatic, aerial and social environments.

2. Environmental Degradation

Land disturbance by construction activities has resulted in soil erosion increases from two to 40 000 times the pre construction rates (8) with sediment being the principal transport mechanism for a range of pollutants entering water courses (12). The global concern regarding the contamination of the environment by soil erosion in agricultural lands, urban wastes and by-products of rural, industrial and mining industries are increasing. The majority of these contaminants are high levels of chemicals by products and heavy metals, which can affect flora, fauna and humans living in the vicinity or downstream of the contaminated sites. Table 1 shows the maximum levels of heavy metals tolerated by environmental and health authorities in Australia and New Zealand (2).

Concerns about the spreading of these pollutants have resulted in strict guidelines being established globally for the decontamination and rehabilitation of these sites. Methods used in these situations have often been to treat the contaminants chemically, burying or to remove them from the site. These methods are expensive and at times impossible to carry out, as the volume of contaminated material in most cases is very large, examples are gold and coal mine tailings.

Table 1: Investigation threshold levels for potential soil contaminants set by ANZECC/NHMRC (1992) and Chemical Hazards and Emergency Management (CHEM) Unit (1991) .

If these wastes cannot be economically treated or removed, off-site contamination must be prevented. Wind and water erosion and leachate are often the causes of off-site pollution. An effective erosion and sediment control program can be used to rehabilitate such sites. Vegetative methods are the most practical and economical, however, revegetation of these sites is often difficult and slow due to the hostile growing conditions present which include toxic levels of heavy metals.

These contaminations are particularly acute in the rapidly developed economies of developing countries where resources are not adequate to provide satisfactory solution to the problem. As VGT has been shown to be a natural, effective, low tech and low cost alternative means of solving the problem, it is therefore ideally suited not only for the developing countries but also globally for the protection of the environment.

3. Some Special Attributes of Vetiver Grass

The following characteristics make vetiver an ideal species for environmental protection:

• Vetiver grass has neither stolons nor rhizomes but a massive finely structured root system, reaching 3-4m in the first year. This massively thick root system reinforces the soil and at the same time makes it very difficult to be dislodged under high velocity flows (9,11).

• Stiff and erect stems, which form dense hedges when, planted close together. These hedges can stand up to relatively deep-water flow, reduces flow velocity and traps sediment (20).

• Highly resistance to pests, diseases and fire (34).

• Tolerance to extreme climatic variation such extreme temperature from

• Tolerance to prolonged drought, submergence and flood (31).

• Highly tolerant to growing medium high in acidity, alkalinity, salinity, sodicity and magnesium (23,26).

• Highly tolerant to Al, Mn, As, Cd, Cr, Ni, Pb, Hg, Se and Zn in the soils (26, 27).

• High level of tolerance to herbicides and pesticides (5, 15)

• Highly efficient in absorbing dissolved N, P, Hg, Cd and Pb in polluted water (15, 17).

• Ability to regrow very quickly after being affected by the above adverse conditions after growing conditions improved or soil ameliorants added (20).

4. Protection of the Terrestrial Environment

4.1 Agriculture

4.1.1 Soil erosion and sediment control on sloping farmlands

Both research and field results in Australia Asia, Africa and South America show that in comparison with conventional cultivation practices, surface runoff and soil loss from fields treated with vetiver were significantly lower and crop yield was much improved. The yield increase was attributed mainly to uniform in situ soil and moisture conservation over the entire toposequence under the vetiver hedge system (19).

4.1.2 Erosion and sediment control on floodplain

VGT has been used as an alternative to strip cropping practice on the flood plain of Queensland. This practice relies on the stubble of previous crops for erosion control of fallow land and young crops. On this experimental site, vetiver hedges that were established at 90m interval provided a permanent protection against flooded water. Results over the last five years, (including several major flood events) have shown that VGT is very successful in reducing flood velocity and limiting soil movement, with very little erosion in fallow strips (6, 7, 24).

The incorporation of vetiver hedges as an alternative to strip cropping on floodplains has resulted in more flexibility, more easily managed land and more effective spreading of flood flows in drought years and with low stubble producing crops. An added benefit is that the area cropped at any one time could be increased by up to 30% (3).

4.1.3 Rehabilitation Saline and Acid Sulfate Soils

The spread of salinity in both dryland and irrigated lands are of major concerns in low rainfall and semiarid regions of the world. Vetiver has been used very successfully in erosion control and rehabilitation of these salt-affected lands (23).

Acid Sulfate Soils (ASS) constitute a major component of arable lands in many tropical countries in Africa and Asia such as Thailand and Vietnam where rice is the main food crop. These soils are highly erodible and difficult to stabilise and rehabilitate. Eroded sediment and leachate from ASS are extremely acidic. The leachate from ASS has led to disease and death of fish in several coastal zones of eastern Australia. Vetiver has been successfully used to stabilise and rehabilitate a highly erodible acid sulfate soil on the coastal plain in tropical Australia, where actual soil pH is around 3.5 and oxidised pH is as low as 2.8 (22, 26).

4.1.4 Bioremedial

Vetiver has played an important role in the retention and decontamination of agro-chemicals especially pesticides, preventing them from contaminating and accumulating in the soils and crops.

Research conducted in cabbage crops grown on steep slope (60%) in Thailand indicated that vetiver hedges had an important role in the process of captivity and decontamination of agrochemicals especially pesticides such as carbofuran, monocrotophos and anachlor, preventing them from contaminating and accumulating in the soils and crops (15, 17).

4.1.5 Biological pest control

Research conducted at Guangxi University, China (3), showed that of the 79 species of insect found on the vetiver rows, only four attacked young vetiver leaves. However due to their small population the damage was minimal. On the contrary, 30 other species found in the vetiver rows are considered beneficial insects, as they are the all-important prey enemy of garden, agriculture and forest pests. This indicates that an Integrated Pest Management scheme will be put into operation when vetiver is introduced to a new environment.

In Thailand, methanol extracts of ground stem and root were found to be very effective in preventing the germination of a number of both monocotyledon and dicotyledon weed species. These results indicate the potential of vetiver extract as a natural pre-emergent weedicide (18).

4.2 Natural Disaster

4.2.1 Typhoons (Cyclones or Hurricanes)

Trees take several years to develop extensive and deep root systems necessary to anchor the soil on steep slope to prevent land slides and reduce erosion, whereas, vetiver grass when properly established can provide the same effect within 12 months.

Due to the El Nino effects, a series of hurricanes, particularly Mitch and Georges, devastated several countries in Central America in 1998, causing floods and landslides, cutting off highways and other severe infrastructure damages also killing several people. Damage assessment carried out after the typhoons revealed that VGT provided a very effective protection against high rainfall, high wind and floods. Both civil construction structures such as roads, dams etc and farmlands remained stabled if they were protected by VGT. As a result of that observation, the World Bank sponsored a workshop on the bioengineering application of VGT in San Salvador, El Salvador in May 1999. Participants from several countries in Central and South America and speakers from El Salvador, Mexico, Venezuela and Costa Rica evaluated the effectiveness and exchanging experience on the application of VGT for the protection and stabilisation of infrastructure in the region (14).

4.2.2 Landslide

Landslides are often caused by the lack of structural strength of the ground on steep slopes and the event is triggered by the over saturation during heavy rainfall periods. The problem can be exacerbated by the presence of tall trees, which can be overtopped by strong wind. Under natural conditions such as forests, deep rooted trees provides the structural reinforcement, but when deforestation is carried out for agriculture and forestry production or infrastructure construction, this structural protection is lost. When this occurs, landslide often resulted, a good example of this effect is found in Madagascar (25).

A common type of landslide, known in Madagascar as Lavaka where the whole hillside collapses. The size of Lavaka varies but it can be up to 300-500m high and 200-300m wide. The main factors contributed to the initiation of Lavaka are:

• Deforestation

• Highly erodible soils which have very deep and unstructured profiles

• Overgrazing and burning before the rainy season

• Concentrated runoff, which is intensified by pasture burning and high intensity rainfall from early season storms.

Of all these causes, the only rehabilitation method that is feasible, practical and socially acceptable is to reduce concentrated runoff, which can be effectively spread out by vetiver hedges. This involves planting overlapping short hedges to spread and divert runoff water away from the actively eroded Lavaka heads. When the hedges are fully established, the concentrated flow would be either spread out or diverted to a more stable area, rehabilitation works on the eroded land below the head can be started by using vetiver grass first and either native or Eucalyptus trees later.

4.2.3 Floods

The combination of the deep root system and thick growth of the vetiver hedges will protect the banks of rivers and streams under flood conditions. Its deep roots prevent it from being washed away while its thick top growth reduces flow velocity and its erosive power. In addition, when properly laid out hedges can be designed to direct water flow to appropriate area (31).

Very successful stream bank and riverbank stabilisation has been carried out in Australia, Malaysia and the Philippines.

Vietnam is now very interested in using VGT to stabilise the extensive Red River dyke system, which was built over centuries to protect the Red River delta in North Vietnam from annual flooding. This delta is presently protected by 5 000km of dyke, 20% of which is damaged every year during the rainy season, this translates to 1 000km of dyke which needs repair every year. The engineer in charge admitted that rock baskets (mattress/gabions), which he called Chinese technology, did not work as they were always washed away when the earthen bank collapsed under them. He added that the Red River is now full of rocks from previous attempts over the year's (28).

4.3 Infrastructure

The most rapid impact of VGT in the last four years has been in area of steep slope stabilisation for infrastructure protection. This follows Diti Hengchaovanich’s presentation of the results of his works in Malaysia at the last Vetiver Conference in Chiang Rai in 1996. In addition to Malaysia (9,10), two other countries that have adopted VGT for infrastructure stabilisation on a very large scale are China and Madagascar.

Following the International Vetiver Workshop in October 1997 in Fuzhou, China, the Fujian Highway Bureau officially accepted vetiver for standard highway embankment stabilisation. Subsequently this Bureau formally issued a memorandum asking all highway institutions through out the province to study vetiver technology and to use the grass to protect the embankments (36, 37, and 38). In October 1999, due to great interest shown by other provinces recently, the China Vetiver Network again organised an International Conference on Vetiver Bioengineering Technology for Erosion and Sediment Control in Civil Construction in Nanchang.

In Madagascar, following the visits by Dick Grimshaw in 1997 and Paul Truong in 1998 and under the leadership of Criss Juliard, VGT has become the leading technology in road and highway stabilisation in that country and is now being applied to all roadwork investments and is fully endorsed by the Madagascar Society of Engineers. Several rural road systems and railways are now protected by VGT. With this momentum, VGT will be the main technology protecting the Madagascar road and highway networks in the near future (Juliard, pers.com.).

Other countries have also rapidly adopting VGT for infrastructure protection are Australia, the Philippines, El Salvador and several other Central American countries (30).

4.4 Mining

On site and offsite pollution control from mining wastes is another major breakthrough in the application of VGT for environmental protection. Research conducted by this author over the last 6 years has clearly established the extremely high levels of tolerance of vetiver grass to Al, Mn, As, Cd, Cr, Ni, Cu, Pb, Hg, Se and Zn in the soils (Table 2) (26).

Table 2: Threshold Levels of Heavy Metals to Vetiver Growth (27).

NA not available

Table 3 shows that distribution of heavy metals in vetiver plant can be divided into three groups:

• very little of the arsenic, cadmium, chromium and mercury absorbed were translocated to the shoots (1% to 5%),
• a moderate proportion of copper, lead, nickel and selenium were translocated ( 16% to 33% ) and
• zinc was almost evenly distributed between shoot and root ( 40% ).

The important implications of these findings are that when vetiver is used for the rehabilitation of sites contaminated with high levels of arsenic, cadmium, chromium and mercury, its shoots can be safely grazed by animals or harvested for mulch, as very little of these heavy metals are translocated to the shoots. As for copper, lead, nickel, selenium and zinc their uses for the above purposes are limited to the thresholds set by the environmental agencies and the tolerance of the animal concerned.

In addition, although vetiver is not a hyper-accumulator it can be used to remove the some heavy metals from the contaminated sites and disposed off safely elsewhere, thus gradually reducing the contaminant levels. For example, vetiver roots and shoots can accumulate more than 5 times the chromium and zinc levels in the soil.

Table 3: Average Distribution of Heavy Metals in Vetiver Shoots and Roots.

These results have led the two major mining countries, Australia (Poster) and South Africa, to increasingly adopting VGT as a major component of their rehabilitation strategy.

In Australia, VGT is highly successful in the rehabilitation of old quarries and mines where very few species can be established due to the hostile environment. Vetiver is able to stabilise the erodible surface first so other species can colonise the areas between hedges later. After two years, the site was completely revegetated with vetiver and local species (20). In Queensland, vetiver has been successfully used to stabilise mining overburden and highly saline, sodic and alkaline tailings of coal mines (16) and highly acidic (pH 3.5) tailings of a gold mine. Recently VGT has been used to rehabilitate bentonite mine wastes and tailings dam walls of a major bauxite and copper mines and alumina refinery in northern Australia (27).

In South Africa, rehabilitation trials conducted by De Beers on both tailing dumps and slimes dams, at several different sites, have found that vetiver possessing the necessary attributes for self-sustainable growth on kimberlite spoils (13). Vetiver grew vigorously on kimberlite, containing run off, arresting erosion and creating an ideal micro-habitat for the establishment of indigenous grass species. At Premier (800mm annual rainfall) and Koffiefonteine (300mm rainfall) diamond mines where surface temperature of the black kimberlite often exceeds 55^oC, at this temperature most seeds are unable to germinate. Vetiver planted at 2m VI provided shades that cool the surface and allowing germination of other grass seeds (Grimshaw pers.com.). more recently very successful rehabilitation of slimes dams has also been carried out at Foskor mines.

Vetiver is being used to rehabilitate a large copper mine in China and coal mines in Indonesia.

4.5 Landfill and Contaminated Lands

Old landfill, and industrial waste dumps such as tanneries, galvanised factory and electrolytic factories are usually contaminated with heavy metals such as As, Cd, Cr, Hg, Pb and Zn. As these heavy metals are highly toxic to human, the movement of these metals off-site must be controlled.

The erosion at an old landfill site at Cleveland in Australia is a great concern to the local community as contaminated materials and leachate polluted adjacent ground and watercourses. The landfill was capped with 1m of topsoil and successfully rehabilitated with local vegetation but the sides slopes (70%) which remained bare of vegetation for over 20 years due to high levels of heavy metals and other toxic chemicals. These slopes were highly erodible (21).

Rehabilitation works was carried out by planting vetiver rows on the side slopes for erosion control. For leachate control, vetiver was planted en masse at the toe of the slope where leachate appeared. Although the landfill was contaminated (Table 4), vetiver established easily and grew well with N and P application at planting. The slopes were completely stabilised within 12 months and local vegetation established naturally between the hedgerows. During the same period, leachate export was reduced substantially during the wet season and was eliminated during the dry season. When the slope was stabilised, native tree and shrubs were planted to complete the rehabilitation works. In this application vetiver acted as a pioneer plant.

Table 4: A typical heavy metal profile of the old landfill at Cleveland.

*values exceeds permitted levels.

On the same principles thick stand of vetiver has been used in Australia to soak up sub surface effluent drained from septic tanks and intensive animal farms such as piggeries, cattle feedlot and dairy farms.

In China, similar results were obtained in Guangzhou, where rehabilitation was quickly achieved with vetiver planting. The effectiveness of vetiver in purifying urban garbage leachate was compared with Alternanther philoxeroides, Paspaulum notatum and Eichhornia crassipes. On the whole, the results showed that the growth of Vetiver in high concentrated leachate (HCL) and its purification of HCL was much better than other species. Of the seven parameters measured in the study, ammoniac nitrogen was the best cleansed, and its purification rate was between 83% - 92%. In addition, vetiver showed a quite high purification rate for phosphorus (more than 74%) (35).

Similarly, in Thailand vetiver was successfully used to rehabilitate a landfill site near Bangkok .

5. Protection of the Aquatic Environment

5.1 Purification of Polluted Water

In China research showed that vetiver can reduce soluble P up to 99% after 3 weeks and 74% of soluble N after 5 weeks. With proper planning VGT has the potential of removing up to 102t of N and 54t of P per year per hectare of vetiver planting (39).

5.2 Control of Algal Growth in Rivers and Dams.

As soluble N and particularly P are usually considered to be key elements for water eutrophication which normally leads to blue green algal growth in inland waterways and lakes, the removal of these elements by vegetation is a most cost effective and environmental friendly method of controlling algal growth.

Chinese works indicated that vetiver could remove dissolved nutrients and reduced algal growth within two days under experimental conditions (35, 39). Therefore, VGT can be used very effectively to control algal growth in water infested with blue-green algae. This can be achieved by planting vetiver on the edges of the streams or in the shallow parts of the lakes where usually high concentrations of soluble N and P occurred. Alternatively vetiver can be grown hydroponically on floating platforms which could be moved to the worst affected parts of the lake or pond. The advantages of the platform method is that vetiver tops can be harvested easily for stock feed or mulch and vetiver roots can also be removed for essential oil production.

5.3 Removal of Heavy Metals

Works in Thailand showed that VGS could absorb substantial amount of Cd, Hg and Pb in waste water (17). Therefore can be effectively used for the following applications:

5.4 Effluent Disposal

With the potential of removing very high quantity of N and P, vetiver planting can be used to remove P, N and other nutrients in effluent from sewage, abattoirs, feedlots, piggeries and other intensive livestock industries. In Australia VGT was used very successfully as an integral part of an waste water purification program in removing nutrient from effluent from septic tanks.

5.5 Trapping Agrochemicals and Nutrients

When established across drainage lines and watercourses, vetiver hedges filter and trap both coarse and fine sediment resulting in cleaner runoff water.

In Australia the combination of vetiver and African star grass have filtered out both bed and suspended load of runoff water on a pineapple farm in Queensland. Sediment load was reduced from 3.94g/L to 2.33g/L after passing through the hedge, and similarly, electrical conductivity was reduced to half (263uSm/cm to 128uSm/cm). The high dose of weedicide used did not affect vetiver growth (6). In other trials on sugarcane and cotton farms, vetiver hedges planted across drainage lines were particularly efficient in trapping particulate sediment containing high concentration of nutrients and agrochemicals. In sugar cane farms 69% of P in runoff sediments were trapped and on a cotton farm from 67% to 90% of pesticides, 48% of herbicides, 52% of P, 73% of N and 55% of S were trapped (32).

5.5 Wetland Application

In the early 1970’s Professor Kikuth in Germany pioneered the use of wetland plants for wastewater treatment. Since then various forms of wetland have been used around the world to treat anything from sewage (primary, secondary and tertiary) to effluent from chemical and heavy industries. For example reed plants (Phragmites spp) have been used successfully for remediation of ground water contaminated with petrochemicals and also effluent from a large steelwork in the UK (1).

As vetiver thrives in wetlands, it is therefore highly suitable for use in the wetland system to remove pollutant from industrial as well as agricultural wastes such as nutrients and agrochemicals from polluted water discharged from cropping lands and aquaculture ponds. Recent research in Australia also demonstrated that vetiver can tolerate extremely high level of Atrzine and Diuron, under wetland conditions. At the concentration of

2 000ug/L, while other wetland plants, including Phragmites australis were either killed or their growth was severely reduced, vetiver growth was not affected by these two chemicals, which are the most two commonly used weedicides in sugarcane farm in Australia (5).

In the US, researchers have recently reported that Vertical Flow Wetland (VFW) and Horizontal Flow Wetland (HFW) cells planted with vetiver, respectively, removed 98% and 96% total suspended solids (TSS), 91 and 72% total chemical oxygen demand (COD) and 81 and 30% dissolved COD from sludge derived from a trout farm. Both wetland types removed most, 82-93%, of the dissolved phosphate, total Kjeldahl nitrogen and total phosphate.

6. Protection of the Aerial Environment

6.1 Dust Pollution Wind

When dry, the finely ground mine tailings material is easily blown away by wind storms if not protected by a surface cover. As gold tailings are often contaminated with heavy metals, wind erosion control is a very important factor in stopping the contamination of the surrounding environment. The usual method of wind erosion control in Australia is by establishing a vegetative cover, but due to the highly hostile nature of the tailings, revegetation is very difficult and often failed when native species are used. The short-term solution to the problem is to plant a cover crop such as millet or sorghum, but these species only last for a few years. Vetiver can offer a long-term solution, when planting in long rows at appropriate spacing to reduce wind velocity and at the same time provide a less hostile environment (eg shading and moisture conservation) for local native species to establish voluntarily later.

In a trial comparing the effectiveness of vetiver hedges and wind barriers in controlling dust storms and promoting the establishment of ground cover on a 300ha gold tailings dam, vetiver has proved to be far superior and much cheaper than the wind barrier and equally effective in promoting grass establishment. Vetiver growth after the first year was 1.5m tall and has survived several windstorms, which flattened several sections of the wind barrier in the last 12 months.

6.2 Vetiver Grass and Greenhouse Gas

Vetiver grass offers a means to benefit the earth’s atmosphere as well as its terrestrial environment. Vetiver can sequesters large quantities of carbon dioxide from the atmosphere but nobody yet knows how much greenhouse gas vetiver can remove, but a rough estimate can be gained from measurements made on a closely related grass, Andropogon guyanus. In 1995, CIAT (International Agricultural Research Institute in Colombia) reported that this species and another deep-rooted African grass grow so widely and so prolifically in the savannas of South America that they "may remove as much as 2 billion tons of carbon dioxide from the atmosphere yearly." Andropogon guyanus roots penetrate 1 meter into tropical soils and CIAT scientists found that the plant sequesters as much as 53 tons of carbon dioxide as organic matter per hectare per year (33).

Vetiver roots, by contrast, are more extensive and penetrate tropical soils to depths of 5 meters and beyond. Its rate of absorbing the gas is likely to be at least twice that of its botanical cousin. Approximate calculations suggest that a single vetiver plant may absorb 2 kg of C0₂ a year (33).

7 Protection of the Social Environment

VGT also exerted a beneficial effect on the socio-economic aspect of rural life in the Philippines. Due to the prolonged drought, which was caused by El Nino, in the last few years, there was no work for rural farming communities. This often led to the break up of rural families as people moved to the cities to find work. The need to supply planting materials for various infrastructure projects in rural area, Vetiver Farm Inc., in Manila was able to provide employment for local people in propagating and planting vetiver near their villages. Therefore VGT provided opportunities for these people to remain in their villages instead of drifting to the big cities looking for work (29). 

8. Conclusion

As most of the developments and applications mentioned above have been developed in the last four years, since the last International Vetiver Conference, there is no doubt that with the present momentum the impact of VGT on the global scene will continue and will become the main technology for environmental protection.

9. References

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