Pursuing energy generation from biomass is crucial to complementing investments in seasonal hydropower
SEP 24 –
Recently, the government of Nepal signed a Project Development Agreement for the 900 megawatt Upper Karnali Hydropower project with an Indian company. Since then, has been much discussion on the development of hydropower projects. To supplement these discussions and debates amongst hydropower specialists and policymakers, it is important to seek complementary options to diversify electricity generation, given the mostly seasonal behaviour of hydropower, the huge investment requirements, and potential uncertainties related to natural calamities such as landslides.
Loadshedding—due to high electricity demand coupled with the low capacity of run-of-the-river type hydroelectric plants from a meagre generation capacity with less than 2 percent of the total potential—has been posing a serious threat to the country’s economic and industrial development. Despite several government initiatives to deal with the energy crisis, such as the formation of taskforces and action plans along with the ambitious target for not only meeting domestic electricity demand but also exporting the surplus hydroelectricity to India, the problem of electricity supply remains the same, with increasing blackouts.
There is no doubt that the country’s medium and long-term objectives should be to harness its abundant hydroelectricity potential. But it is equally important to explore other indigenous renewable sources in consideration of the security of energy supply, energy diversification and sustainability. In this regard, biopower or biomass power, is renewable energy gleaned from biomass resources.
Nepal produced around 4.5 million tonnes of paddy and 2.9 million tonnes of sugarcane in 2012-13. With few supply chain and logistics difficulties associated with the collection and transport of agricultural residues in the Tarai—where 99 percent of sugarcane and 70 percent of paddy are grown—bagasse and rice husk, the by-products of sugar and rice milling, can be used for energy (heat and power) generation. Around 70 percent of total sugarcane comes to sugar mills and the rest is diverted for the production of local sweeteners—chaku and shakhar. With the adoption of state-of-the-art technologies, these primary agricultural residues can be used to produce bioelectricity (biopower) for connection to the national grid or to meet domestic and industrial energy demands.
Under present conditions, bagasse cogeneration—the use of heat engines to generate both useful heat and energy—is not efficient. Installation of high pressure boilers and turbines in sugar mills could generate around 308GWh of surplus bioelectricity, with an installed capacity of 85 MW when cogeneration runs during the crushing period, especially in the dry season (December-April). Similarly, considering the husk-to-paddy ratio of 0.2, the total rice husk available for energy production is 0.63 million tonnes per year in the Tarai. The corresponding clean electricity generation potential from husk power plants stands at around 75 MW, providing 660 GWh of clean energy per year. This biopower can be used for rice milling, providing electricity access to rural communities or running micro-industries.
Depending on the size of rice mills, different capacity small-scale gasifier plants can be installed for electricity generation. For example, gasifiers in the range of 50-500 kW can be installed for rice milling capacities ranging from 2.5 quintals/hour to 25 quintals/hour.
Similarly, Nepal also produces around 1,550 tonnes (per day) of solid waste in 58 municipalities (excluding the newly created ones), which can produce 10 MW of clean and reliable power through the waste-to-biogas conversion route. Derived electricity can be used to power urban centres and industries. Biogas can also be upgraded as transport fuel or used as cooking gas.
Long dry seasons coupled with run-of-the-river type hydropower plants and uneven energy demands during the day are key reasons for extended hours of loadshedding in Nepal. In the dry season, hydropower plants produce far less electricity. They are subject to seasonal river flows and cannot provide electricity in their full capacity. Therefore, the diversification of energy sources is indispensable, not only to secure energy supply and to meet seasonal imbalance but also to guarantee availability and the optimisation of natural resources.
Since the dry season and sugarcane milling operations coincide, the complementarity of the two renewable sources is apparent, facilitating the exploration of this untapped biopower opportunity. Biopower could provide 1,054 GWh of electricity (around 25 percent of total electricity production in Nepal), equivalent to 120MW of clean and renewable electricity in 2012. This is much higher than the amount of electricity import (746 GWh) from India. Biopower from domestic renewable biomass could also help reduce accumulated financial losses due to the import of electricity. Besides, biopower can avert carbon emissions and air pollution. Bioelectricity could serve peak hours, provided that there are facilities to store agricultural residue (bagasse and rice husk).
Bioelectricity has great potential to grow in line with the continuous development of the agro-industries, not only through a more efficient conversion of huge amounts of bagasse and rice husk for energy generation, but also through synergy with agricultural development. Sugarcane is a major cash crop for Nepal. But farmers are often disgruntled with low prices, leading to difficulties in smooth supply and operation of sugar mills. This has affected the economic condition of farmers and the country’s sugar demands are unmet.
The sale of biopower from bagasse cogeneration or rice husk gasifiers could definitely help strengthen the efficient operation of the agricultural and industrial sectors. The use of molasses—another by-product in sugar industries—for fuel ethanol production in distilleries can also help increase the performance of the sector. Similarly, paddy farmers can benefit if rice husk is used for energy production. Bagasse electricity and molasses ethanol can help to stabilise the sugar industry even if the price of sugar remains low. The energy produced can even be used for irrigation. Moreover, agricultural productivity or yield, as well as industrial performance, can simultaneously increase when the sector becomes economically attractive.
Biomass, therefore, must be prioritised. Initial investments on efficient conversion technologies, viz. cogeneration, gasifiers, and anaerobic digestion plants to generate biopower are high. So government support and incentives need to be provided. The technologies are already available and biopower is being commercially produced in several countries. For example, India and Brazil have been quite successful at implementing bagasse cogeneration. The neighbouring Indian state of Bihar has implemented husk power systems in rural villages using a ‘Pay for Use’ business model. Similarly, waste to biogas has already been developed as a proven technology. Appropriate government policies, along with the creation of proper market conditions for bioelectricity sales and grid connection, should be put in place for biopower implementation.
Khatiwada holds a PhD in Energy Technology and is a postdoctoral researcher at the KTH Royal Institute of Technology, Sweden
Source : eKantipur