Energy Efficiency in Agrifood Systems

Introduction

The International Energy Agency (IEA) considers energy efficiency as “the world’s first fuel”. Incorporated into the new global political agenda as a “Sustainable Development Goal”, energy efficiency is key for climate protection and overcoming resource shortages. Thus, identifying and solving efficiency gaps is crucial for sustainable development.

Efficiency is defined as the ratio of the desired output to the required input of any system. However, it is determinant to distinguish between quality and quantity of output service, which makes evaluating and quantifying efficiency a difficult task. On a global scale, more than half of the worldwide consumption of primary energy is lost in production processes by transport and general energy consumption. As two thirds of global greenhouse gas emissions (GHG) derive from energy consumption, energy efficiency is crucial for climate change mitigation. Increasing energy efficiency can also lead to co-benefits, e.g. increasing security of energy supply, improving import quality, increasing productivity and economic growth, and modernizing facilities.

Further, introducing energy efficiency measures can improve global food security. Since global food demands will increase with a growing world population, also will respective energy needs. The agri-food sector strongly depends on energetic inputs, which reveals the importance of finding solutions to improve energy efficiency along agricultural value chains.

Technologies

Energy efficiency implies reducing energy needs by using sustainable technologies or by splitting the energy input among different uses. Sometimes simple improvements in apparently insignificant steps of the production process can sum up and lead to considerable energy efficiency and cost savings.

Depending on the activity, different technologies and measures can improve energy efficiency. For example, heat supply may be required in greenhouse farming and further processing. Waste heat can be recovered here by using heat exchangers that capture the waste heat for pre-heating other processes, or to insulate pipelines, building facilities, etc. For cooling processes, using appropriate insulation material and efficient refrigeration systems can help reducing GHG emissions and post-harvest losses. Among irrigation techniques, energy can be saved by using gravity supply, or applying water by drip irrigation. This can also improve (indirect) energy efficiency derived from fertilizer manufacturing, as they can be applied more accurately. In general, using renewable energy will lead to higher energy efficiency and bring co-benefits while lowering GHG emissions, creating access to electricity for agricultural purposes and allowing a modernization of the power grid. Read more…

Energy Efficiency in Agriculture

Agriculture consumes about 30 percent of the global energy and thus, improving energy efficiency in the sector is essential to reduce GHG emissions and energetic dependency on fossil fuels.

In agricultural production, for example, indirect energy inputs in the form of energy-intensive manufactured fertilizers and pesticides present a significant energy saving potential. By introducing Conservation Agriculture approaches such as crop rotation, fertilizer or pesticide application can be reduced, and soil fertility improved. No-till agriculture enhances soil quality and reduces soil GHG emissions, requiring at the same time less direct energy inputs as diesel fuel for ploughing machinery.

Another energy gap where productivity and efficiency can be improved is irrigation. When substituting diesel pumps with solar powered pumps, fuel dependency and its derived costs can be reduced considerably.

Within the food processing industry, cooling and heating are essential steps with high energy consumption and energy saving potentials. Improvements to technical elements and usage of modern refrigeration systems have the potential to reduce energy consumption by 15 to 40 percent. Introducing renewable energy for solar cooling systems or biomass-powered refrigerators can reduce GHG emissions from processing. Changing technologies and improving management and operations can reduce energy demand along the value chain. Read more…

Cogeneration

One of the most promising technologies within the energy efficiency approaches is Cogeneration or Combined Heat and Power (CHP), which uses a heat engine to simultaneously generate both electricity and useful heat. When, additionally, cooling energy is provided by the system, it is referred to as Trigeneration. In most heat engines, more than 50 percent of the primary energy is wasted as excess heat. By capturing the excess heat, an aggregate efficiency of 80 to 95 percent can be reached. Cogeneration technology is applicable in a wide range of sectors and bares a high potential within the agriculture context: by employing cogeneration technology, food processing plants can utilize biomass by-products to generate heat and power, which in return can be used for the production process. For example, within the sugarcane industry, the bagasse residue from sugar refining can be burned to produce steam. Sent through a turbine, the steam turns a generator, and produces electric power. This again, can serve to supply the electric energy demand needed to operate the plant and generates a surplus that can be commercialized. For instance, cogeneration plants are commonly found in central heating systems for hospitals, hotels and industrial plants with large heating needs adding to their electricity demand. Cogeneration encompasses a wide range of proven technologies.

In general, there are two basic principles for cogeneration: a topping cycle, where electricity is first produced, to then use the heat derived from electricity production, and a bottoming cycle, which produces high amounts of heat, which can be recovered and fed into an electrical plant. Waste heat recovery and thus cogeneration can be operated in all types of combustion processes and fuels. Advantages of cogeneration lie in its high efficiency gains of 30 percent and more, resulting from one single generation process of power and heat, and the reduction of emissions, costs and fuel dependency. Read more…

Case Studies

Energy Efficiency Potentials in the Kenyan Tea Sector

Kenya is one of the leading tea producers and exporters worldwide: its tea industry has had an annual growth rate of 4 percent in the past 10 years and generated the biggest capital share of the Kenyan agricultural sector, which accounts for 65 percent of all export revenues. However, tea processing requires intensive energy inputs, being often unsustainable and quite expensive. The high energy saving potential of the Kenyan tea sector has motivated Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH to enter a development partnership with the UK-based company Betty’s and Taylors of Harrogate and Kenya Tea Development Agency Holdings Ltd. (KTDA). Together, they aim to improve energy efficiency by generating knowledge about economically feasible investments, which save energy, mitigate GHG emissions and increase productivity. Read more…

Within tea production, the highest amounts of energy are required for drying and withering. However, there are many more steps along the value chain that can be optimized, ensuring maximum efficiency and reducing energy requirements and production costs significantly.

Female tea farmer in Kenya (©Böthling)

Boiler Operation

Boiler operation can be enhanced by opening the boiler door only when filling, removing ash daily, eliminating leakages in the steam and condensate system, etc. Further, when feeding the boilers with properly billeted wood, a higher efficiency will be reached during combustion, reducing overall energy requirements. Fuel wood billeting is the process of chopping wood into smaller regular sized pieces with increased surface area.

Seasoning

Seasoning is the process of drying wood to reduce moisture content. The benefits of proper seasoning include reduced wood consumption, efficient boiler operation and reduced smoke. Withering uses around 40 percent of a factory’s total electricity consumption and over 50 percent of total thermal energy consumption, making it the most energy intensive process in the tea factory. Using fans and warm air can help to keep energy consumption to a minimum.

Cut, Tear, Curl

Cut, Tear, Curl (CTC) operations account for 20 percent of total factory electricity consumption, which can be reduced by different energy saving measures like sharpening the CTC rollers, reducing friction of the rollers, ensuring machinery is well maintained, etc.

Drying

After withering, tea drying is the second most intensive process requiring 40 percent of the factory’s heat and 20 percent of electricity requirements. Opportunities to reduce energy here are ensuring the equipment and fans are cleaned after use, air dampeners are set at the correct angle between the wet and dry end of the dryers to reduce resistance, air intake is well controlled, etc.

Fermentation

Finally, fermentation also requires heat and electricity, although in smaller amounts, which can be reduced by ensuring uniform thickness of tea on the fermentation bed to minimise air requirements, keeping steam use to a minimum.

Have Improved Cookstoves Benefitted Rural Kenyans?

Cooking accounts for an estimated 2 percent of all greenhouse gas emissions worldwide, and cooking using firewood produces 45 percent of the CO2 emissions attributed to cooking. EnDev Kenya, a division of GIZ (the German development agency), has been promoting improved cookstoves (ICS) since 2006 in collaboration with the government of Kenya, nongovernmental organizations, and private firms.

They promote two types of energy-efficient and improved cookstoves: the Jiko Kisasa, 40 percent more efficient, and the Rocket stove, 20 percent more efficient. Both are produced locally, use firewood, and have no chimneys but provide good combustion. As of December 2017, about 9.6 million people had benefitted from it. According to EnDev, ICS lowered firewood consumption by 638,000 tons (corresponding to 38,000 hectares of forest) and cut CO2 emissions by more than 738,000 tons between 2016 and 2017. On average, the improved cookstoves reduced fuel consumption by about 20-32 kg a month (about 18-29 percent of consumption). As ICS adoption reduced the time women spent collecting biomass fuels by 92-105 minutes a week, it also increased the time women spent on income-generating activities, childcare, and leisure. Furthermore, ICS reduced some of the symptoms associated with exposure to household air pollution. It has also helped to develop the cookstove market in rural Kenya, creating jobs in the production, marketing and installation of stoves. Some 4,200 previously unemployed people (mostly women and youth) have become self-employed in the ICS market. Read more…

Publications & Tools

Energy Auditing

Energy Auditing is a tool to identify energy efficiency potential and measures and assessing their financial viability. This can be done at a simple level by a brief site inspection assessing the broad energy input and output of a system and identifying low cost energy saving opportunities. Medium level audits include in-depth analysis of energy costs, energy usage and system characteristics along with on-site energy demand measurements to identify which energy measures need to be aligned with the financial budget plan of the site. Investment grade audits are the most sophisticated level and include additional continuous monitoring of system data and process characteristics. Energy audits are the first step for introducing and establishing energy management systems (EMS) in enterprises and enable efficient management of energy demand and consumption in production or processing entities – also in agricultural value chains. Energy audits include four phases, starting with an energy use review, followed by a site assessment, which examines all system components and their performance, a data analysis, and the audit report. Energy audits allow finding suitable energy efficiency measures and result in economic and environmental improvements. Read more…