Enhancing economic benefits and resilience through pyrolysis based coffee drying

Published: 28th March 2017 16:09Last Updated: 2nd June 2017 10:17
How the installation developed during the Pulpa Pyro Peru project is transforming coffee production in Vietnam


The processing of coffee produces large quantities of waste in the form of pulp. This waste, which is moist and slightly acid, is not conducive to composting and fermentation; it is also not suitable for fodder or fuel. As a result, thousands of tons of coffee pulp worldwide are not valorized, and so are left to rot because of a lack of proper treatment. These rotting piles of pulp, which are foul-smelling, pose a significant environmental and health risk. They release the potent greenhouse gas (GHG) methane, thereby contributing to climate change, and contaminate seeping water, leading to the pollution of local water sources. At the same time, this pulp contains a lot of potassium - a valuable mineral fertilizer - that the coffee tree has pulled from the soil. 

Ökozentrum Langenbruck and Sofies-Emac AG implemented this project with financial support from REPIC. REPIC is a joint instrument of the Swiss Agency for Development and Cooperation (SDC), the Swiss State Secretariat for Economic Affairs (SECO), the Federal Office for the Environment (FOEN) as well as the Swiss Federal Office of Energy (SFOE). The project developed a way of valorizing coffee pulp by using pyrolysis technology to convert it into renewable energy, which can be used in the coffee production line, and biochar, which can be used as a natural fertilizer and soil enhancer. This technology provides economic to benefits farmers through increasing productvity and quality of their crop: The renewable energy is used to effectively dry the coffee crop, so that crop losses are reduced and the overal quality of the crop is improved; the biochar by-product can be used to improve the soils, thereby increasing productivity and reducing the need for expensive fertilizer. Biochar also sequesters carbon. Combined with the generation of renewable energy, this has the potential to transform coffee production into a carbon neutral, and possibly even carbon negative process, thus reducing sector contributions to future climate change.

Although applied here to the coffee sector, the technology developed and transfered under this project is also appropriate for waste-to-power and energy generation from other harvest residues on small to midsize farms

This appraoch is described in detail in an initial project description "Pyrolysis for coffee pulp valorization" by Jürg Schmidlin, Hannes Zellweger and Martin R. Schmid, and the final report "Pulpa Pyro Peru - Clean generation of biochar and energy from coffee pulp", by Martin R. Schmid. The sections below borrow significantly from these reports.

Methods and Tools

The Pulpa Pyro Peru: small mobile installation for the pyrolysis of wet coffee pulp project developed a mobile installation for pyrolytic combustion that is simple to use and maintain, and that can be operated continuously. The video above features a project started in Vietnam to integrate the installation developed during the Pulpa Pyro Peru project into the entire coffee production process. 

Farmer's needs

Farmers need effective, cost-effective methods of 'disposing' of piles of coffee pulp waste. They also need on-site and in-time energy to process the coffee in order to sell the coffee pre-pealed and dried (in Peru this is called “café pergamino”). This means that the coffee still contains the silver skin or hard shell but is dryed to 12% total water content. This requires additional fuel to provide heating for the drying process. There is also a need for fertilizer: In Peru the farmer has to decide between spending roughly 1000 US$ per hectare and year for fertilizer or live with significant less harvest.

Advantages of Pyrolysis

The technology component of the joint global UNIDO-UNEP Resource Efficient and Cleaner Production (RECP) program, identified pyrolysis as a potential technology for step-reductions in terms of byproduct treatment and their valorization. The main advantages are as follows:

  • Production of renewable energy (biogas), which can be used for the drying process with a reduction of traditional thermal energy consumption of around 40-70%. In Peru the drying process is usually the bottleneck and key for coffee quality. Poor drying conditions mean that some of the collected coffee crop may rot, leading to crop losses and reduced quality. Improvements in drying are thus key for securing farmers' incomes. 
  • Reduced need for wood, coffee husks or fossil energy and hence a reduction in CO2 emissions and potentially reduced deforestation.
  • Fast, appropriate and clean solution for coffee pulp “disposal”, reducing the potential environmental and health risks associated with large piles of waste pulp.
  • Production of Biochar, which can improve soil characteristics, especially of tropical soils, to achieve higher yields and save money through reducing the use of expensive and scarce fertilizer.
  • Carbon sequestration - biochar is also regarded as a carbon sequester.

Research and design of a mobile pyrolysis plant

Five assessments in three typical coffee growing regions in Peru were undertaken. During these it was soon realized that a stationary pyrolysis plant would not be economically feasible because of the short harvest seasons and therefore short operational time.

The main factor for the time of year of the harvest is altitude. In Peru coffee is grown at altitudes 800-1500 metres above sea level. Thus a mobile plant, which can be easily driven to different altitudes, could be run almost throughout the year. Knowing that the pyrolysis plant can be also used in other agro-industrial sectors i.e. cacao, banana, sugar cane, gives exiting options for different business models.

To meet these needs the FLOX®-burner was selected, where exhaust gases are recirculated for heating. Although still comparatively new, it had already been applied in biomass torrefaction. As there was no such mobile pyrolysis plant commercially available, a prototype plant was developed with the target of processing 90 kg coffee pulp per hour.

Simplified biochar field tests 

While there is abundance of information available on biochar and its effects on soil, there is little knowledge on its specific application and benefits in the coffee growing sector. As biochar is one of the main benefits of the pyrolysis plant it is important to estimate its effects on the coffee plant. In consequence a plan for simplified biochar field tests was elaborated and in 2014, a scientific full size plantation test was started in Peru in which an array of young coffee bushes were given a variety of mixtures of compost and biochar and monitored for crop productivity and soil GHG emissions.

Technology transfer and practical implementation

Often, projects are made with technology that is hard to understand and too difficult to repair, resulting in unavoidable failure over time. To avert this in Peru, a local “coffee processing machinery” company was involved and consulted during the project. Before the final technical drawings were created, a “technology transfer mission” with the key engineer, who is responsible for the fabrication of the plant, was held. This ensured the local availability and understanding of the proposed technologies, materials and spare parts.

After successful testing if the prototype installations during winter 14/15, a workshop brought together local machine manufacturers from both Peru and Vietnam to disseminate the project results more widely. A professional documentary film team accompanied the workshop and produced a very helpful and informative short video which was distributed to all project partners (see video below). At the end of the workshop, a tour was organized to see a farm in central Switzerland, which already applies pyrolysis and uses the biochar in different ways in the barn, in the manure and to produce new soil (humus). The two delegations returned to their countries with a full documentation of the full size prototype and the knowledge to adapt the technology according local needs. 

To support further work beyond the initial project, the CharNet.ch network (http://charnet.ch/) was set up in late 2015. CharNet is a network of professionals in Switzerland to support biochar and coordinate the research demand. Among the more than 70 private members, companies, farmers and institutions there are research teams of EAWAG, ZHAW, FiBL, Agroscope, Ithaka-Institute and Ökozentrum. 

Outcomes and Impacts

In Peru the installed system exceeded expectations:

  • The combustion gases contain far fewer pollutants than the quantities defined by the limit values ​​of the Swiss Federal Ordinance on Protection of Air (OPair);
  • the plant processes 80 kg per hour of wet pulp and provides 40-70 kW of heat for drying;
  • the plant also weighs less than 600 kg in total, meaning that it can be transported on a standard pick-up vechicle;
  • operation requires less than 1.5 kW. 
  • The plant carbon has passed the European Biochar Certificate (EBC) test. 

With the support of the consulting company Sofies-Emac AG, the success of this project has been additionally increased. Only six weeks after the workshop, the first photographs arrived from Vietnam, showing their plant in production. 

The first results of the soil benefits from the scientific full size plantation test in Peru are encouraging in terms of reduced emission levels. No significant increase in growth or productivity was observed; however, this is expected as biochar acts to improve soil structure and nutrient retainment, but in order to see immediate benefits the biochar requires nutritional 'charging' before use. This and the flexibility of the newly developed process has increased the interest in this technology within Switzerland.