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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy Science and Technology".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 41669

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Prof. Dr. Joachim Müller

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Institute of Agricultural Engineering, University of Hohenheim, 70593 Stuttgart, Germany
Interests: solar energy; bioenergy application in agriculture; postharvest processing; irrigation technology; efficient water and energy use; renewable energy; expertise covers systematic design (VDI 2221); computer-aided engineering (CATIA); computational fluid dynamics (ANSYS); transient systems simulation (TRNSYS); machine vision; hyperspectral imaging
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Dr. Hans Oechsner

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State Institute of Agricultural Engineering and Bioenergy, University of Hohenheim, D-70599 Stuttgart, Germany
Interests: bioenergy; biogas process; trace elements for biogas; pretreatment of substrates; drying of digestate; efficiency of biogas processes; BMP test methods; energy crops; AD of organic waste; platform chemicals
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Against the background of the discussion on climate change, renewable energies have experienced an enormous increase in public interest. In this context, agriculture plays a doubly important role: both as a consumer and as a provider of renewable energy. Rural areas in many regions are only sparsely supplied with energy networks, and the agricultural sector can benefit from easy access to (micro)hydropower; wind energy; solar energy; and, of course, bioenergy. In addition to meeting its own energy needs, agriculture can act as an energy supplier by producing biomass, biodiesel, bioethanol, and biogas. Public and private research funding has led to a considerable increase in research and development activities in this field. This Special Issue is intended to bring together the latest findings of the researchers in order to initiate new research based on the state of the art. We invite you to submit your recent research addressing one of the following topics:

Production and processing of energy crops;
Provision of solid biofuel, biodiesel, bioethanol and biogas;
Processing and use of biogas digestate;
Combustion and pyrolysis of biomass;
Engines and stoves for vegetable oil;
Solar heating in agriculture;
Solar drying of agricultural products;
Solar cooling of agricultural products;
Solar desalination of irrigation water;
Agro-photovoltaics;
Photovoltaic pumping of irrigation water;
Wind and water driven pumps in agriculture;
Renewable energy in greenhouse applications;
Modelling and simulation;
Life cycle assessment;

Prof. Dr. Joachim Müller
Dr. Hans Oechsner
Guest Editors

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Keywords

energy crops
solid biofuels
biodiesel
bioethanol
biogas
Solar heating
Solar drying
Solar cooling
Solar desalination
Agro-photovoltaics
Photovoltaic pumping
Micro hydropower
Wind energy
Modelling
Life cycle assessment

Published Papers (12 papers)

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Research

16 pages, 1623 KiB

Open AccessArticle

Assessment of Areal Methane Yields from Energy Crops in Ukraine, Best Practices

by Ievgeniia Morozova, Hans Oechsner, Mykola Roik, Benedikt Hülsemann and Andreas Lemmer

Appl. Sci. 2020, 10(13), 4431; https://doi.org/10.3390/app10134431 - 27 Jun 2020

Cited by 8 | Viewed by 2218

Abstract

Growing and utilizing bioenergy crops as feeding substrates in biogas plants may aid the development of the biogas sector in Ukraine. Therefore, research was done on potential methane yields from 22 high-yield varieties of 7 different crops grown in Ukraine for their biogas production suitability. Annual crops (maize, soybean, sweet sorghum and sorghum hybrids) and perennials (miscanthus, paulownia and switchgrass) harvested at three different harvesting times (H1, H2 and H3) related to specific stages of phenological development were investigated. The perennial crops studied were from different vegetation years. The samples were analysed in Ukraine on their dry matter- and volatile solids contents, dry matter yield (DMY) and crop nitrogen (N) uptake. The 55 °C -dried samples were delivered to Germany for their analysis with the Hohenheim Biogas Yield Test (HBT) on their specific methane yield (SMY). Based on DMY and SMY, the areal methane yields (AMY) were calculated. The highest SMY and AMY were found for maize, sweet sorghum and miscanthus. The highest average SMY of 0.35 ± 0.03 m³_CH4 kgVS⁻¹ was found for maize samples harvested at H2. Miscanthus “Giganteus” from the 8th vegetation year harvested at H1 has shown the highest AMY of 7404.50 ± 199.00 m³_CH4 ha⁻¹. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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13 pages, 4820 KiB

Open AccessArticle

Drying Performance and Aflatoxin Content of Paddy Rice Applying an Inflatable Solar Dryer in Burkina Faso

by Sebastian Romuli, Steffen Schock, Marius Kounbèsiounè Somda and Joachim Müller

Appl. Sci. 2020, 10(10), 3533; https://doi.org/10.3390/app10103533 - 21 May 2020

Cited by 8 | Viewed by 3630

Abstract

The drying performance of paddy rice using an inflatable solar dryer (ISD), or also known as GrainPro^® Solar Bubble Dryer™, was evaluated and compared to conventional sun drying in Burkina Faso. Drying time was around eight hours. Thermal imaging was conducted to observe temperature distribution in the ISD during drying and mixing. Shadow casting was observed in the ISD due to the round shape of the black plastic film, which reduced the temperature of the paddy rice to about 10 °C. The temperature inside the ISD was up to 13 °C higher than the ambient temperature, whereas the temperature of paddy rice on the top layer was about 5 °C higher than on the bottom. The final moisture content of paddy rice dried in the ISD and under the sun was not considerably different. Under certain circumstances, impurities in paddy rice dried in the ISD could be substantially lower than for sun drying. The aflatoxin level of paddy rice was under the maximum limit of the EU regulation. Drying paddy rice seemed to be effective to remove aflatoxin type AFG2 content. Further adaptation of the ISD design for drying operations on rough surfaces and sandy soils is suggested. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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12 pages, 1021 KiB

Open AccessFeature PaperArticle

Potential of Biogas Production from Processing Residues to Reduce Environmental Impacts from Cassava Starch and Crisp Production—A Case Study from Malaysia

by Jens Lansche, Sebastian Awiszus, Sajid Latif and Joachim Müller

Appl. Sci. 2020, 10(8), 2975; https://doi.org/10.3390/app10082975 - 24 Apr 2020

Cited by 20 | Viewed by 4222

Abstract

The cultivation of cassava (Manihot esculenta) is widely spread in a variety of tropical countries with an estimated annual production of 291.9 million tons. The crop is the most important source of carbohydrates in producing countries. In Malaysia, cassava is mainly cultivated for starch production. Despite the economic and nutritional importance of cassava, there is only limited knowledge available regarding the overall environmental impacts of cassava starch production or the production of alternative food products like cassava crisps. This study presents an environmental assessment of different scenarios of cassava production and processing by a life cycle assessment (LCA) approach. The results indicate that the environmental impacts of cassava-based products can be reduced considerably with the utilization of processing residues for anaerobic digestion if the resulting biogas is used for the production of electricity and heat. In the industrial scenario, the results indicate that the highest relative reductions are achieved for cumulated energy demand (CED), global warming potential (GWP) and deforestation (DEF) with −39%, −26% and −18%, respectively, while in the advanced scenario, environmental impacts for CED, GWP, ozone formation potential (OFP) and water stress index (WSI) can be reduced by more than 10% with −281%, −37%, −16% and −14%, respectively. The impacts for global warming potential found in this study are slightly higher compared to other studies that focused on the carbon footprint of starch production from cassava, while the savings due to biogas production are similar. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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18 pages, 1825 KiB

Open AccessFeature PaperArticle

Biomethane Potential Test: Influence of Inoculum and the Digestion System

by Benedikt Hülsemann, Lijun Zhou, Wolfgang Merkle, Juli Hassa, Joachim Müller and Hans Oechsner

Appl. Sci. 2020, 10(7), 2589; https://doi.org/10.3390/app10072589 - 09 Apr 2020

Cited by 42 | Viewed by 5327

Abstract

High precision of measurement of methane potential is important for the economic operation of biogas plants in the future. The biochemical methane potential (BMP) test based on the VDI 4630 protocol is the state-of-the-art method to determine the methane potential in Germany. The coefficient of variation (CV) of methane yield was >10% in several previous inter-laboratory tests. The aim of this work was to investigate the effects of inoculum and the digestion system on the measurement variability. Methane yield and methane percentage of five substrates were investigated in a Hohenheim biogas yield test (D-HBT) by using five inocula, which were used several times in inter- laboratory tests. The same substrates and inocula were also tested in other digestion systems. To control the quality of the inocula, the effect of adding trace elements (TE) and the microbial community was investigated. Adding TE had no influence for the selected, well- supplied inocula and the community composition depended on the source of the inocula. The CV of the specific methane yield was <4.8% by using different inocula in one D-HBT (D-HBT1) and <12.8% by using different digestion systems compared to D-HBT1. Incubation time between 7 and 14 days resulted in a deviation in CV of <4.8%. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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12 pages, 7759 KiB

Open AccessArticle

Mechanical Harvesting Line Setting of Giant Reeds

by Alberto Assirelli, Vincenzo Civitarese, Giuseppina Caracciolo, Maura Sannino and Salvatore Faugno

Appl. Sci. 2019, 9(24), 5425; https://doi.org/10.3390/app9245425 - 11 Dec 2019

Cited by 7 | Viewed by 2285

Abstract

This study evaluated the possibility of adopting haymaking farming machinery in giant reed (Arundo donax L.) harvesting. The test shows the technical and energy aspects of mechanical harvesting using only one specific machine, a shredding machine, designed and developed by an Italian constructor for large biomass herbaceous crops (giant reed, sorghums, switchgrass, Mischantus, etc). It is designed for high vegetative growth crops, as it is able to spread products over all soil surfaces or, alternatively, carry out windrowing. Tests were conducted in the south of Italy (Campania region) on the experimental farm Torre Lama in Bellizzi (SA). Biomass was shredded, dried in the field, and baled for use in a logistic chain and storage. The first step was the cutting and shredding of biomass crops with the specific shredder rear-mounted in an agricultural tractor. The biomass then was dried on the field, constantly monitored for moisture content, and finally, baled with a trailed round baler for storage (second step) and used in a specific logistic chain. The test showed good performance of the shredder machine between 1.17 and 1.77 ha h⁻¹ with an operative speed between 3.9 and 5. 9 km h⁻¹. To define the hourly production, a high wet production level of 60.70 t ha⁻¹ and a low level of 56 t ha⁻¹ were used as references. Under the climatic conditions of the experimental test, this harvesting system showed some advantages, such as the possibility of immediate and long-term biomass storage (less than 14% moisture content), the potential alternative use of the biomass, and the reduced resource use compared to that of other ordinary crops growing in the area. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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22 pages, 5364 KiB

Open AccessArticle

Development and Experimental Results of a Thermal Oil Based Roasting System for Decentralized Processing of Groundnuts

by Ali Raza, Faizan Majeed, Anjum Munir and Oliver Hensel

Appl. Sci. 2019, 9(20), 4342; https://doi.org/10.3390/app9204342 - 15 Oct 2019

Cited by 5 | Viewed by 2612

Abstract

The current research has been conducted to investigate the capacity of an indigenously developed thermal oil based continuous solar roaster (CSR) for groundnuts roasting. A 10 m² standing Scheffler fixed focus concentrator is used to target the incoming direct normal irradiance at casted aluminum surface of a heat receiver which transfers this heat energy to the roasting unit by means of thermal oil circulation. The roasting unit comprises a cylindrical shell (2000 mm in length and 450 mm in diameter) attached beneath a semi-circular oil flow jacket and equipped with a ribbon type screw conveyer with 6 mm thick paddles. Optimizing for maximum energy utilization and feeding capacity using response surface methodology, roasting time for light, medium and dark quality was found to be 14 + 0.1, 20 + 0.1 and 29 + 0.1 min respectively. In terms of roasting quality, CSR has shown quite satisfactory results. The study revealed that continuous solar roaster has the capability to roast 140 to 288 kg groundnuts per day subjected to dark to light roasting quality with average direct normal irradiance ranging from 650–800 Wm⁻². The overall thermal efficiency of the system was found to be 37.8%. The payback period of CSR was estimated to be 2450–5250 useful working hours. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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11 pages, 452 KiB

Open AccessArticle

Chemical Composition and Biogas Formation potential of Sida hermaphrodita and Silphium perfoliatum

by Hanna Siwek, Małgorzata Włodarczyk, Ewa Możdżer, Marek Bury and Teodor Kitczak

Appl. Sci. 2019, 9(19), 4016; https://doi.org/10.3390/app9194016 - 25 Sep 2019

Cited by 22 | Viewed by 2948

Abstract

Biogas production and use is one of the pillars of the EU strategy for fossil fuels replacement via renewable energies. In Poland, the most commonly used crop for biogas production is maize. There are many factors limiting the cultivation of this crop, which is why alternative plants are sought. The aim of the present paper was to assess the effect of establishing a plantation using seeds, seedlings, and various harvest dates on biogas production from Silphium perfoliatum L. (Silphium) and from two phenotypes of Sida hermaphrodita L. Rusby (Sida). Harvesting was conducted in the second (2017) and third year of crop growth (2018). These crops were harvested in June and at the beginning of October as a two-cut strategy. Additionally, Silphium was harvested in early autumn as a one-cut strategy. Specific biogas yield (SBY) and specific biomethane yield (SMY) were estimated using the modified Baserga method. The biogas yield per hectare (BY) was calculated. The crop species, method of establishing a plantation, as well as the date and the number of harvests had a significant effect on the content of the selected chemical components; however, significant differences in terms of SBY were not found for the two-cut strategy. In the case of Silphium, approximately 40% more BY was produced for the two-cut strategy compared to the one-cut strategy. The BY was found to be significantly affected by the biomass yield; markedly higher BY can be obtained from Silphium and the average amount obtained in one year was 8598 m³ ha⁻¹ while 4759 m³ ha⁻¹ was obtained from Sida. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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20 pages, 2579 KiB

Open AccessArticle

Research on Optimal Dispatching Strategy for Micro-Energy-Grid of Protected Agriculture

by Yuntao Ju, Mingxin Jin, Jiankai Wang, Jianhua Yang, Mingyu Dong, Dezhi Li, Kun Shi and Haibo Zhang

Appl. Sci. 2019, 9(18), 3929; https://doi.org/10.3390/app9183929 - 19 Sep 2019

Cited by 8 | Viewed by 2228

Abstract

With the growth in demand for energy and the boom in energy internet (EI) technologies, comes the multi-energy complementary system. In this paper, we first model the components of the micro-energy-grid for a greenhouse, and then analyzed two types of protected agriculture load: time-shifting load and non-time-shifting load. Next, multi-scenario technology is directed against the uncertainty of photovoltaic (PV). Latin Hypercube Sampling (LHS) and the backward reduction algorithm are the two main methods we use to generate the representative scenarios and their probabilities, which are the basis for PV prediction in day-ahead scheduling. Third, besides the time of day (TOD) tariff, we present a model using real-time pricing of consumers’ electricity load, which is proposed to compare consumers’ demand response (DR). Finally, we establish a new optimization model of micro-energy-grid for greenhouses. By calculating the dispatch of electricity, heat, energy storage and time-shifting load under different conditions, the local consumption of PV and the comprehensive operational cost of micro-energy-grid can be analyzed. The results show that a storage device, time-shifting load and real-time pricing can bring more possibilities to the micro-energy-grid. By optimizing the time schedule of time-shifting load, the cost of the greenhouse is reduced. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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15 pages, 2821 KiB

Open AccessArticle

Experimental Verification of Yam (Dioscorea rotundata) Drying with Solar Adsorption Drying

by Emmanuel Amankwah, Gloria Kyere, Herbert Kyeremateng and Anton van Boxtel

Appl. Sci. 2019, 9(18), 3927; https://doi.org/10.3390/app9183927 - 19 Sep 2019

Cited by 7 | Viewed by 3607

Abstract

This work evaluates the yam (Dioscorea rotundata) drying performance of solar adsorption drying (SAD) compared to solar drying (SD) and open sun drying (OSD). The evaluation concerns the drying cycle for batches of yam, the effect on vitamin C, color and composition. As SAD can be applied during the night, by using air dehumidified by passing through a bed of silica gel, the cycle time for drying batches of yam can be reduced over 20–25% compared to SD and halved compared to OSD. SAD is thereby most effective during the first nights of drying when the driving force is the highest. Composition was not affected by drying methods but did affect vitamin C content. Vitamin C retention is not significant different for SD and SAD, but with a slight preference for SD. For three yam cultivars (‘Pona’, ‘Lilii’ and ‘Dente’), ‘Lilii’ dried fastest and ‘Dente’ drying slowest. SAD maintained 16 the whitish color of yam better than the other drying methods. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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11 pages, 3327 KiB

Open AccessArticle

Technical Performance of an Inflatable Solar Dryer for Drying Amaranth Leaves in Kenya

by Sebastian Romuli, Steffen Schock, Marcus Nagle, Christine G. Kiria Chege and Joachim Müller

Appl. Sci. 2019, 9(16), 3431; https://doi.org/10.3390/app9163431 - 20 Aug 2019

Cited by 11 | Viewed by 4113

Abstract

The technical performance of an inflatable solar dryer (ISD) to dry amaranth leaves (Amaranthus spp.) was investigated. To handle the drying of lightweight materials, modification was made by adding an air deflector and trays inside the ISD. Computational performance of the ISD solar energy system was evaluated using MATLAB Simulink. The estimated air mass flow in the inlet of the ISD was 0.75 kg/s. Using computational fluid dynamics (CFD), the uniformity of air distribution in the ISD was evaluated. The solar radiation reported during good drying performance ranged between 510 and 950 W/m². In a controlled charging system, a 100 W_p PV module typically generated voltage between 10.22 and 18.75 V. Drying conditions at temperatures of 40 °C or above were typically achieved in the ISD from 12:00 to 16:00. Temperature inside the ISD could reach up to 69.4 °C during the day and 13.4 °C during the night. The highest relative humidity of 97.4% was recorded during the night. Opening the ISD while mixing the product could lead to considerable heat loss. Fluctuation of solar radiation and shaded areas in the ISD appeared to be the major factors affecting the drying performance. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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19 pages, 2134 KiB

Open AccessArticle

Kinetic Modeling and Techno-economic Feasibility of Ethanol Production From Carob Extract Based Medium in Biofilm Reactor

by Mustafa Germec, Irfan Turhan, Mustafa Karhan and Ali Demirci

Appl. Sci. 2019, 9(10), 2121; https://doi.org/10.3390/app9102121 - 24 May 2019

Cited by 26 | Viewed by 4125

Abstract

In this study, different carob extract-based media containing Medium A (included all ingredients), Medium B (included yeast extract and salts), Medium C (included (NH₄)₂SO₄ and salts), Medium D (included only salts) and Medium E (included no ingredients) were evaluated for ethanol fermentation by Saccharomyces cerevisiae in a biofilm reactor and their results were used for kinetic modeling. The logistic model for cell growth, Luedeking-Piret model for ethanol production and Modified Luedeking-Piret model for substrate consumption were studied. Kinetic parameters were determined by fitting the observed values of the models. The findings indicated that the predicted data with the suggested kinetic model for each medium fitted very well the experimental data. Estimated kinetics were also in good agreement with experimental kinetics. The techno-economic analysis was performed with the unit costs of the components used in the medium and ethanol. Medium-based process economic feasibility proved carob extract-based Medium E and subsequently Medium D as most economical for ethanol production. The present study verified the potential of carob extract-based medium for increased economical production of ethanol. In conclusion, the ethanol production in a biofilm reactor is growth-associated since α (gP/gX) was greater than β (gP/gX.h) and Media D and E increased the economic production of carob extract-based ethanol. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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12 pages, 1722 KiB

Open AccessFeature PaperArticle

Physical Properties of Jatropha curcas L. Fruits and Seeds with Respect to Their Maturity Stage

by Sebastian Romuli, Shkelqim Karaj and Joachim Müller

Appl. Sci. 2019, 9(9), 1802; https://doi.org/10.3390/app9091802 - 30 Apr 2019

Cited by 5 | Viewed by 3444

Abstract

Jatropha curcas L. is a multipurpose bioenergy crop. Physical properties of J. curcas fruits and seeds are a fundamental knowledge required for the design of processing machinery. Therefore, this research investigates the physical properties at different maturity stages as indicated by pericarp color of the fruits (green, yellow, and black). Rupture force, hardness, deformation at rupture point, deformation ratio at rupture, and energy used for rupture were measured in the length and width direction of the fruits and in the length, width, and thickness of the seeds. During the course of maturing, a decrease in the unit mass and the surface area of the fruits was observed with a simultaneous increase for the seeds. Moisture content decreased during maturing. Bulk density and solid density were considerably different among maturity stages. The lowest porosity was observed in black fruits as well as “black” seeds. The highest dynamic and static angle of repose was detected for black fruits, while no substantial difference was observed between “yellow” and “black” seeds. The highest and lowest coefficient of static friction for all fruits and seeds was found on rubber and plastic surfaces. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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