Socio-economic microbial process strategies for a sustainable development using environmentally clean technologies: Sagopalm a renewable resource

Horst W Doelle

MIRCEN-Biotechnology Brisbane and the Pacific Regional Network

Abstract

In order to secure health with high life expectancy and to become self-efficient, which means supply and demand for domestic consumption is guaranteed, each government must strive and direct all its efforts towards increasing renewable resource production, thereby maintaining or reducing its demand by diversification of the staple food and at the same time remove health hazardeous wastes. Increased monoculture with a single outlet will continue to cause problems to farmers and the ecological environment. In order to foster de-urbanisation, the farmer has to be offered attractive alternatives, which means security through a change froma mono- to a multiple-product agricultural industry. This alternative must include clean technologies providing the people with a cleaner environment [prevention of infectious diseases], food, feed, fertiliser, fuel as well as energy. In SE Asia and parts of the Pacific Region, the sagopalm (Metroxylon sagu)is a unique renewable resource and was therefore selected for this presentation. The palm grows well in swampy areas unsuitable for other crops, is very suitable for humid tropical low lands and contains an average of 160 kg starch, which can be increased to 275 kg in a well attended farm. This means that an average 25 t of starch/hectare sagopalm cultivation could be obtained. A comprehensive socio-economic integrated biosystem will be presented, whereby the sagopalm farm can be used to supply (1) house building material (2) energy through gasification (3) mushroom production (4) starch flour (5) ethanol for biofuel (6) methane or biogas for energy (7) aquaponics and fish production for food (8) microbial protein for animal feed (9) compost or other residual effluent for organic fertilisation of the farm Such a system would increase self-efficiency on the farm, clean environment through reutilisation of the so-called 'waste' into value-added products and thus greatly increase the income of the farming community.

Key words: Sago palm, biotechnology, starch, biomass

Introduction

Biotechnologies unquestionably generate benefits or gains, but they are also bringers of certain dangers or potential threats. Their impact on societies will be considerable (Doelle et al 1987) and there will be winners and losers. This will depend on which strategies are adopted by the community, country or group of countries. For developing countries, technological independence is highly likely to increase. But it is in their power to design appropriate strategies in order to take advantage of biotechnologies according to their needs, specific situation and constraints. Whilst avoiding imitating the strategies of industrialised countries, the search for appropriate solutions will then lead these countries to participate to the general advancement of scientific knowledge needed for progress in biotechnology (DaSilva and Sasson 1989). Processes which are economical for one nation may well be uneconomical for another irrespective whether these countries are developed or less developed (Doelle 1982). Since all technological developments are aimed at improving the quality of life of a community of people (DaSilva et al 1992), developing countries are looking for programmes reducing the risk to health and achieving sustainable, economical growth conducive to a higher per capita income of the community (Doelle 1996 a,b). It should therefore be our aim not only to detoxify the results of the industrial and green revolutions, but also to reverse the trend of urbanisation in making farming more attractive (Doelle 1989).

In studying and familiarising myself with the nature of tropical and subtropical biomass, society and culture of the developing countries all over the globe over the past 25 years, it became very soon very clear that a transfer of the developed countries industrial economic system strategy will and has to fail as it would lead to a further aggravation of the existing problems. Furthermore, an appropriate biotechnology (Doelle 1982) transfer, which would be similar to the presently advocated 'zero-emission' strategy, could be useful for waste management with social benefits (Chan 1993, 1997a,b), but would still not be able to handle the sustainability of the rural as well as urban communities. I therefore adopted in my teaching and advising the idea of Lewis (1987), that we have to develop a socio-economical system strategy (DaSilva et al 1992; Doelle 1989, 1993, 1994; Doelle et al 1993a) whereby waste management [= appropriate technology = zero emission] must become an integrated part of our new clean technology system. In line with this socio-economical concept I interpret sustainability as "a future mean of a society to be able not only to feed themselves but also to be independent from imports for their basic requirements, which means utilising their own natural renewable resources to furnish them with food, feed, fertiliser, fuel and energy".

Microbial Process Strategies for Sustainability

There should be no doubt in anybody's mind that microorganisms are the most powerful creatures in existence. They determine the life and death on this planet. They can kill merciless, but at the same time they can be harnessed to sustain life. Nature has provided us with a perfect balance in the carbon, nitrogen, sulfur cycles [using microorganisms] to sustain plant, animal and human life. We should therefore always keep in mind (a) it is the microbe which determines the growth and existence of plant, animal and human on this planet; (b) that the microbe is much more flexible and adaptable to environmental changes than plants, animals and humans. Our societies were able to increase life expectancies and wealth in some countries, but managed to foster the killer-type and reducing or eliminating the beneficial type of microorganisms. This trend has to be changed.

The new socio-ecological concept is based on the requirement for full exploitation of a harvested renewable resource and the replacement of monoculture/mono-product farming with a multiproduct system (Doelle et al 1993a). Because it produces a variety of products, this system will hopefully enjoy a constant and reliable market demand and will be able to secure income for the rural sector as well as for joint venture industries (Doelle 1996b). Such a multi-product system must be tailored to the demands of the society in which it will operate and thus will differ from country to country.

Sagopalm

In Southeast Asia and the Pacific, rice, cassava, and sago are the main staple food crops. Of these, sagopalm (Metroxylon sagu) and cassava are inexpensive and not nearly as agriculturally intensive as rice, making them obvious candidates for further diversification and exploitation as starch sources. The palm grows well in swampy areas, which can only be developed for other crops at high cost. It is perennial, very suitable for humid tropical low lands and is already available in areas which are in urgent need of economic development. There exist at present an estimated two million hectares of natural or wild stands of sago palm compared to only 200,000 ha of cultivated sago palm.

Plate 1: Sagopalm [courtesy of Dr.Kopli Bujang, UNIMAS]

The production capacity of the sago palm varies between 2-5 tons of dry starch/ha in the wild to 10-25 t/ha in cultivated crops (Flach 1983). Clump densities of 590 palms/acre or 1480 palms/ha would allow a yearly harvest of 125-140 palms/year (Tan 1983). A well attended farm can produce 175 kg starch/palm, giving a total yield of 25 tons of starch/ha. At present only 3,460 ha of sagopalm are being cultivated, but a total of 61,980 ha are estimated to be available for production (Maamun and Sarasutha, 1987).

After the removal of cortex, rachis and leaflets from the pith, which is probably the most labour intensive part of the sago palm processing, starch has to be extracted from the pith. Whereas the non-pith parts of the sago palm trunk form

• excellent building materials for local and urban houses, sheds or other buildings;
• resources for composting [biofertiliser];
• resources for gasification and energy production;
• resource for animal feed (El-Nawawy 1992; Zadrazil 1992);

the trunks have to be cut into 1 - 1.5 m length for transportation into the regional processing plant.

The pith consists mainly of starch, which has to be separated from the cellulosic cell walls of the trunk. The residue from this starch extraction is a very strong pollutant because of its cellulosic fibrous material. In Indonesia, such material coming from the cassava (=manihot or tapioca), is being used as an animal feed additive. We suggest, however, that it should form the basis for a mushroom industry. Almost purely cellulosic in nature, mushroom would thrive on this waste. The cultivation of edible mushrooms from lignocellulosic and cellulosic residues is well-known (Chang 1980; Chang and Buswell 1996; Chang and Miles 1989; Zadrazil et al 1992) and represents the only current large-scale controlled application of microbial technology for the profitable conversion of agroindustry-waste. A third application would be the use as additional carbon in an anaerobic digester for the production of biogas.

The flexibility, simplicity and low cost alternate usage of the residue not only removes a severe health hazard to the community but, more importantly, increases the self-efficiency of the processing plant and increases the farmer's income through mushroom production.

The starch obtained from the sago palm processing unit can easily be transported to regional centres for further processing. The starch flour or meal can either be used and/or sold for breadmaking or as staple food with the surplus being channelled into further bioprocessing.

Microbial Bioprocessing of starch

The conversion of starch into marketing products requires the conversion of the polymer starch into glucose, which can only be done economically on larger scale using two enzymes, alpha-amylase to loosen the structure of the molecule and thus lowering the viscosity and amyloglucosidase for the final formation of glucose.

Process 1: Enzyme production

The fungus Rhizopus oligosporus, producer of the delicious tempeh food, is a prolific amylase enzyme producer and is known to be free of mycotoxin production, such as aflatoxin. From pilot plant experiments with cassava tuber containing 65% starch it was calculated that 1 ha bearing 65 tonnes cassava tuber can produce 3,500 kg of microbial protein with highly productive amylase enzymes to convert approximately 39,000 tonnes of grain or cassava tuber into glucose (Sukara and Doelle 1989a,b), which is equivalent of a 1200 ha harvest and a glucose yield required for the production of 15.6 million litres ethanol.

Microbial biomass protein (MBP) as well as amylase enzymes could become income-producing products in the local and export markets. At present Indonesia alone spends millions of US dollars for the importation of these enzymes. The aqueous effluent can be used for ponding, as will be outlined below, as it contains only nitrogen and phosphorous with traces of carbon.

Process 2: Ethanol production

Ethanol is gaining an ever increasing importance as fuel additive or even conventional non-renewable fuel replacement. Ethanol is able to reduce significantly the oil import into developing countries or can replace the present fuel allowing the government to save large import costs or increasing the export market of their own oil, both of which will contribute significantly towards a strengthening of foreign currency exchange (Doelle 1994).

There are two technologies available at present, the old traditional yeast [Saccharomyces cerevisiae or others] fermentation and a newly developed bacterial ethanol fermentation technology using Zymomonas mobilis (Doelle et al 1993b) isolated from tropical fruits. Whereas the bacterium allows significantly higher ethanol production rates, produces less biomass, has a higher ethanol tolerance and has a high protein content with a much higher amino acid profile and no glycerol as by-products, the presently operating plants are using the old traditional yeast technology.

The yeast technology converts approx. 90% of all glucose carbons into ethanol with the bacterium increasing this to up to 98%. Whichever technology is used, by-products [some call it wastes] are formed, mainly CO₂, microbial protein and aqueous effluent [or stillage]. Microbial Biomass Protein [MBP] can be used as animal feed additive as the solid residue contains between 30-34% protein, CO₂ can either be compressed to dry ice or transferred into a pond system (see below) for algal cultivation. The stillage can be recycled partly, with yeast only about 30-40% and for the bacterial fermentation up to 80%. Otherwise the stillage contains enough nitrogen and phosphorous to be transferable as biofertiliser or into ponds.

This process therefore would have at least 2 products: ethanol, carbon dioxide as dry ice and microbial biomass protein.

In summary, the sagopalm can provide the community with housing material, bioenergy, mushroom industry, enzyme industry, ethanol, microbial biomass protein for feed, sago flour or meal for food and effluent for biofertiliser.

It should be mentioned here, that glucose is an ideal substrate for all microorganisms and thus can be used to a variety of product formations, including biopolymers such as dextran, antibiotics, acetone, butanol etc., some of which may require a too expensive downstream processing, as well as microbial biomass protein (El-Nawawy 1992).

Process 3: Biogas production

The basic core unit of any socio-economic integrated biosystem should be anaerobic digestion, because the biggest and most health hazardous waste is the animal and human waste. Anaerobic digestion can now be carried out mesophilic (35-40C) and thermophilic (around 50C). Here it is suggested to implement the simplest and most proven technology of mesophilic anaerobic digestion. Depending on the available waste, fermenter sizes in use at present range from a small family 6 m³ to commercial 1500-2000 m³. A very well managed anaerobic digester should produce 1 m³ gas/m³ volume and the biogas mixture should be 70% methane plus 30% CO₂ (Hobson and Wheatley 1993).

Biogas is an excellent energy source and can be used to run generators for electricity production as well as cooking in the households. Biogas behaves similar to natural gas, but has a slightly higher calorific value.

Anaerobic digestion also helps in prevention of infectious diseases caused by pathogens occurring in human and animals wastes. The strict anaerobic conditions required for a successful methane production kills most pathogens responsible for infectious diseases to develop.

Like all processes, anaerobic digestion also has unwanted products as it reduces the COD in general only by 60%. There are solids as well as liquid effluent. Whereas the solids can be used directly as biofertiliser, it would be preferred to be used as an enrichment of composting first before utilising it as a biofertiliser. Composting (Miller 1991; Stentiford and Dodds 1992) adds to the removal of pathogens, making the biofertiliser even safer.

The liquid effluent with its nitrogen and phosphorous content and high alkalinity is an excellent source for algal production, which not only oxygenates the shallow pond but in turn can also be used as an animal and/or fish feed (Thirumurthi 1991; Vonshak 1992; Olguin et al 1994).

Anaerobic digestion not only removes health hazardous waste, but serves as an excellent source of bioenergy, biofertiliser, compost, algae and fish production.

An algal waste treatment process can therefore be converted into a waste utilisation for the production of high-quality protein and in the case of blue-green algae can be made into a biofertiliser production unit to provide nitrogen replacing our chemical fertilisers.

Conclusion

The presented socio-economic process strategy (Figure 1) has as its core unit the biogas production through anaerobic digestion to remove the ever increasing infectious disease outbreaks in developing countries. Most of these countries have no or low efficiency human and animal waste treatment plants. The reasons are variable, often unbelievable, but are a separate discussion theme. With fish resources in the oceans becoming depleted owing to pollution and other adversary effects, fish production and thus aquaculture would benefit from the effluents of anaerobic digestion.

Figure 1: Socio-economic farm cooperative system using Sago palm as renewable resource

A properly managed anaerobic digestion can not only remove the health hazard, but in addition produce energy, alga, fish and other seafood, aquaponics for additional income and higher living standard. In addition the solids used as biofertiliser directly or indirectly via composting will save the community significant amounts of money as it replaces the presently used chemical fertilisers on the field. This organic fertilisation also will improve and regenerate our microbial soil population responsible for the natural cycles of matter, thus improving our soil condition.

The second unit can be flexible depending upon the raw material available. I chose the sagopalm, but the same system can be used for any other starchy crop such as corn, wheat, barley, cassava etc. or sugary substances such as sugarcane (Olguin et al 1995).

The importance is the integration of production and waste management and its simplicity and flexibility. Whether one uses starch or sugar, the changes on the fermentation plant are minimal.

Such a socio-economical integrated biosystem will produce its own fertiliser and could also include biopesticide production. Using nature's own resources and biodiversity, improving the natural cycles of matter for better and higher crop production through farmer incentives, is one of the main goals to achieve sustainability and preservation of our environmental ecology.

In order to secure future food, feed, energy supply, we need renewable resources, which can only be produced by the farming community. A better living standard of the farming community automatically will bring higher living standards to the urban community.

Acknowledgement

I wish to express my most sincere thanks to Dr.Kopli Bujang, Head of the Resource Biotechnology Program in the Faculty of Resource, Science and Technology, UNIMAS, Kota Samarahan, Sarawak, East Malaysia, for the picture of the sagopalm.

References

Received 23 February 1998

Return to top