Biogas from Agricultural Wastes

The main problem with anaerobic digestion of agricultural wastes is that most of the agricultural residues are lignocellulosic with low nitrogen content. To obtain biogas from agricultural wastes, pre-treatment methods like size reduction, electron irradiation, heat treatment, enzymatic action etc are necessary. For optimizing the C/N ratio of agricultural residues, co-digestion with sewage sludge, animal manure or poultry litter is recommended.

Types of Agricultural Wastes

Several organic wastes from plants and animals have been exploited for biogas production as reported in the literature. Plant materials include agricultural crops such as sugar cane, cassava, corn etc, agricultural residues like rice straw, cassava rhizome, corn cobs etc, wood and wood residues (saw dust, pulp wastes, and paper mill waste)

Others include molasses and bagasse from sugar refineries, waste streams such as rice husk from rice mills and residues from palm oil extraction and municipal solid wastes, etc. However, plant materials such as crop residues are more difficult to digest than animal wastes (manures) because of difficulty in achieving hydrolysis of cellulosic and lignocellulosic constituents.

Codigestion of Crop Wastes

Crop residues can be digested either alone or in co-digestion with other materials, employing either wet or dry processes. In the agricultural sector one possible solution to processing crop biomass is co-digested together with animal manures, the largest agricultural waste stream.

In addition to the production of renewable energy, controlled anaerobic digestion of animal manures reduces emissions of greenhouse gases, nitrogen and odour from manure management, and intensifies the recycling of nutrients within agriculture.

In co-digestion of plant material and manures, manures provide buffering capacity and a wide range of nutrients, while the addition of plant material with high carbon content balances the carbon to nitrogen (C/N) ratio of the feedstock, thereby decreasing the risk of ammonia inhibition.

The gas production per digester volume can be increased by operating the digesters at a higher solids concentration. Batch high solids reactors, characterized by lower investment costs than those of continuously fed processes, but with comparable operational costs, are currently applied in the agricultural sector to a limited extent.

Codigestion offers good opportunity to farmers to treat their own waste together with other organic substrates. As a result, farmers can treat their own residues properly and also generate additional revenues by treating and managing organic waste from other sources and by selling and/or using the products viz heat, electrical power and stabilised biofertiliser.

Biomass Exchange – Key to Success in Biomass Projects

Biomass exchange is emerging as a key factor in the progress of biomass energy sector in a particular country. The supply chain management in any biomass project is a big management conundrum. The complexity deepens owing to the large number of stages which encompass the entire biomass value chain. It starts right from biomass resource harvesting and goes on to include biomass collection, processing, storage and eventually its transportation to the point of ultimate utilization.

Owing to the voluminous nature of the resource, its handling becomes a major issue since it requires bigger modes of logistics, employment of a larger number of work-force and a better storage infrastructure, as compared to any other fuel or feedstock. Not only this their lower energy density characteristic, makes it inevitable for the resource to be first processed and then utilized for power generation to make for better economics.

All these problems call for a mechanism to strengthen the value chain. This can be done by considering the following:

  • Assuring a readily available market for the resource providers or the producers
  • Assuring the project developers of a reliable chain and consistent feedstock availability
  • Awareness to the project developer of the resources in closest proximity to the plant site
  • Assurance to the project developer of the resource quality
  • Timely pick-up and drop of resource
  • Proper fuel preparation as per technology requirements
  • Removal of intermediaries involved in the process – to increase value for both, the producers as well as the buyers
  • No need for long term contracts (Not an obligation)
  • Competitive fuel prices
  • Assistance to producers in crop management

The figure below gives a general understanding of how such a model could work, especially in the context of developing nations where the size of land holdings is usually small and the location of resources is scattered, making their procurement a highly uneconomic affair. This model is commonly known as Biomass Exchange

In such a model, the seed, fertilizer shops and other local village level commercial enterprises could be utilized as an outreach or marketing platform for such a service.  Once the producer approves off the initial price estimate, as provided by these agencies, he could send a sample of the feedstock to the pre-deputed warehouses for a quality check.

These warehouses need to be organized at different levels according to the village hierarchy and depending on the size, cultivated area and local logistic options available in that region. On assessing the feedstock sample’s quality, these centers would release a plausible quote to the farmer after approving which, he would be asked to supply the feedstock.

On the other hand, an entity in need of the feedstock would approach the biomass exchange, where it would be appraised of the feedstock available in the region near its utilization point and made aware of the quantity and quality of the feedstock. The entity would then quote a price according to its suitability which would be relayed to the primary producer.

An agreement from both the sides would entail the placement of order and the feedstock’s subsequent processing and transportation to the buyer’s gate. The pricing mechanisms could be numerous ranging from, fixed (according to quality), bid-based or even market-driven.


The hurdles could be in the form of the initial resource assessment which could in itself be a tedious and time consuming exercise. Another roadblock could be in the form of engaging the resource producers with such a mechanism. Since these would usually involve rural landscapes, things could prove to be a little difficult in terms of implementation of initial capacity building measures and concept marketing.


The benefits of  a biomass exchange are enumerated below:

  • Support to the ever increasing power needs of the country
  • Promotion of biomass energy technologies
  • Development of rural infrastructure
  • Increased opportunities for social and micro-entrepreneurship
  • Creation of direct and indirect job opportunities
  • Efficient utilization of biomass wastes
  • Potential of averting millions of tonnes of GHGs emissions


In India alone, there has been several cases where biomass power projects of the scale greater than 5 MW are on sale already, even with their power purchase agreements still in place. Such events necessitate the need to have a mechanism in place which would further seek the promotion of such technologies.

Biomass Exchange is an attractive solution to different problems afflicting biomass projects, at the same time providing the investors and entrepreneurs with a multi-million dollar opportunity. Although such a concept has been in existence in the developed world for a long time now, it has not witnessed many entrepreneurial ventures in developing nations where the need to strengthen the biomass supply chain becomes even more necessary.

However, one needs to be really careful while initiating such a model since it cannot be blindly copied from Western countries owing to entirely different land-ownership patterns, regional socio-political conditions and economic framework. With a strong backup and government support, such an idea could go a long way in strengthening the biomass supply chain, promotion of associated clean energy technologies and in making a significant dent in the present power scenario in the developing world.

7 Crop Health Metrics That Matter to Farmers

Crop health is of paramount importance to farmers; thus, careful and consistent monitoring of crop health is an absolute must. A recent study on coffee yield losses from 2013 to 2015 revealed that pests and diseases led to high primary (26%) and secondary (38%) yield losses in the researcher’s sampled area. This highlights the significance of closely paying attention to such detrimental factors in your crop’s environment. Doing so will ensure maximum yield and profit for farmers come harvest time.

To look at crop health monitoring as governed by just one or two aspects, however, is a serious mistake. Rather, a holistic approach must be adopted; in other words, more factors need to be monitored than just pestilence and disease.

Here are seven of the most important crop health metrics for farmers to monitor, based on the Sustainable Agriculture Research & Education (SARE) Program’s guidelines.

1) Crop appearance

Perhaps the most obvious indicator of crop health is their general appearance. While not an all-in-one, foolproof method of gauging the current condition of a particular set of crops, a farmer possessing the right tools and knowledge can tell quite a lot from simply looking at the state of his or her plants.

Lightness or discoloration in foliage more often than not points to chlorosis, a state in which plants produce insufficient chlorophyll. Modern methods of crop health monitoring, including new technologies that utilize both near-infrared and visible light, allow farmers to actively and accurately monitor chlorophyll content.

2) Crop growth

Among the indicators of poor crop growth are short branches, sparse stand, and the rarity or absence of new shoots. This, of course, will inevitably affect your total yield in a negative way. Under ideal circumstances, there should be robust growth and dense, uniform stand in your crops.

3) Tolerance or resistance to stress

Simply put, crop stress is a decrease in crop production brought about by external factors. An example would be exposure to excess light and high temperatures, which may disrupt photosynthesis (known as photoinhibition). As a result, crops will have insufficient energy to bear fruit or grow, and may even sustain lasting damage to their membranes, chloroplasts, and cells. Healthy crops are stress-tolerant, and can easily bounce back after being exposed to stressors in their environment.

4) Occurrences of pests and/or diseases

An indicator that your crops are extremely susceptible to pests and diseases would be if over 50% of the population ends up getting damaged by said factors. Under the right circumstances, less than 20% of your crops would be negatively affected by any invasion of pests or spread of disease, allowing them to easily recuperate and increase in number once more.

Building crop resistance against harmful insects and diseases can be done in a number of ways, including improving crop diversity, crop rotation, using organic pesticides such as Himalayan salt spray and eucalyptus oil, and even genetic research and enhancement.

5) Weed competition and pressure

Apart from insects and plant diseases, weeds can also spell doom for your crops, if left unchecked. In the event that your farm becomes overpopulated with weeds that will steal the nutrients from your crops, you will certainly notice that your crops are steadily dwindling. Healthy crops, on the other hand, would eventually overwhelm the weed population and reclaim dominance over your field.

6) Genetic diversity

To have only one dominant variety of crop in your farm is tantamount to putting your eggs in a single basket. For instance, you should consider the importance of having multiple disease-resistant crop varieties on your farm. Don’t fall prey to the temptation of replacing them entirely with a single, higher-yielding type.

It is essential to buil crop resistance against harmful insects and diseases

7) Plant diversity and population

In an ideal setting, there should be more than two species of plants in your field. Counting the actual number of trees or plants across your farm, as well as the naturally occurring vegetation on all sides of the area, can also give you a better perspective on your farm’s overall crop health.

Importance of crop management system

Some farmers become overly reliant on insecticides and other chemicals to eliminate their pest problems — a grievous error, as this will likely lead to even more serious problems. Even the indiscriminate application of mineral fertilizers may inadvertently boost pest populations by making conditions ideal for them to thrive.

Ultimately, a combination of the right knowledge and the proper technology is a must in measuring and monitoring crop health metrics. Farmers must always be aware of the current health of their crops, and must be prepared to address any problems with solutions that don’t end up causing more.

Solid Waste Management in South Asia: Key Lessons

swm-south-asiaSolid waste management is already a significant concern for municipal governments across South Asia. It constitutes one of their largest costs and the problem is growing year on year as urban populations swell. As with all waste management experiences, we have learned lessons and can see scope for improvement.

Collection and Transportation

There are two factors which have a significant impact on the costs and viability of a waste management system as it relates to collection and transportation: first, the distance travelled between collection and disposal point; and second, the extent to which ‘wet’ kitchen waste can be kept separate from dry waste much of which can be recycled. Separating waste in this way reduces the costs of manual sorting later on, and increases the prices for recyclable materials.

In many larger towns distances become too great for door-to-door collectors to dispose waste directly at the dump site. Arrangements are made to dispose of waste at secondary storage points (large skips) provided by the municipality. However, where these are not regularly emptied, the waste is likely to be spread beyond the bins, creating a further environmental hazard.

Ideally, and if suitable land can be found, a number of smaller waste disposal sites located around a town would eliminate this problem. With significant public awareness efforts on our part, and continual daily reminders to home-owners, we were able to raise the rate of household separation to about 60%, but once these reminders became less frequent, the rate dropped rapidly back to around 25%. The problem is compounded in larger cities by the unavailability of separated secondary storage bins, so everything is mixed up again at this point anyway, despite the best efforts of householders.

If rates are to be sustained, it requires continual and on-going promotion in the long term. The cost of this has to be weighed against the financial benefit of cleaner separated waste and reduced sorting costs. Our experience in Sri Lanka shows how important a role the Local Authority can play in continuing to promote good solid waste management practices at the household level.

Home Composting

Our experience with home composting shows that complete coverage, with every household using the system, is very unlikely to be achieved. Where we have promoted it heavily and in co-operation with the Local Authority we have found the sustained use of about 65% of the bins. Even this level of coverage, however, can have an important impact on waste volumes needing to be collected and disposed of. At the same time it can provide important, organic inputs to home gardening, providing a more varied and nutritious diet for poor householders.

Waste to Compost and Energy

The variety of technologies we have demonstrated have different advantages and disadvantages. For some, maintenance is more complicated and there can be issues of clogging. For the dry-fermentation chambers, there is a need for a regular supply of fresh waste that has not already decomposed. For other systems requiring water, quite large amounts may be needed. All of these technical challenges can be overcome with good operation and maintenance practices, but need to be factored in when choosing the appropriate technology for a given location.

The major challenge for compost production has been to secure regular sales. The market for compost is seasonal, and this creates an irregular cash flow that needs to be factored in to the business model. In Bangladesh, a significant barrier has been the need for the product to be officially licensed. The requirements for product quality are exacting in order to ensure farmers are buying a product they can trust. However, the need for on-site testing facilities may be too prescriptive, creating a barrier for smaller-scale operations of this sort. Possibly a second tier of license could be created for compost from waste which would allow sales more easily but with lower levels of guarantees for farmers.

Safe Food Production and Consumption

Community people highly welcomed the concept of safe food using organic waste generated compost. In Sri Lanka, women been practicing vertical gardening which meeting the daily consumption needs became source of extra income for the family. Female organic fertilizer entrepreneurs in Bangladesh are growing seasonal vegetables and fruits with compost and harvesting more quality products. They sell these products with higher price in local and regional markets as this is still a niche market in the country. The safe food producers require financial and regulatory support from the government and relevant agencies on certification and quality control to raise and sustain market demand.

The concept of safe food using organic waste generated compost is picking up in South Asia

The concept of safe food using organic waste generated compost is picking up in South Asia


Solid waste management is an area that has not received the attention it deserves from policy-makers in South Asia nations. There are signs this may change, with its inclusion in the SDGs and in many INDCs which are the basis of the Paris Climate Agreement. If we are to meet the challenge, we will need new approaches to partnerships, and the adoption of different kinds of systems and technologies. This will require greater awareness and capacity building at the Local Authority level. If national climate or SDG targets are to be met, they will need to be localised through municipalities. Greater knowledge sharing at national and regional levels through municipal associations, regional bodies such as SAARC and regional local authority associations such as Citynet, will be an important part of this.

Practical Action’s key messages for regional and national policy makers, based on our experience in the region in the last 5 years, are about the need for:

  • creating new partnerships for waste collection with NGOs and the informal sector,
  • considering more decentralised approaches to processing and treatment, and
  • recognising the exciting potential for viable technologies for generating more value from waste