Biomass Production Systems Research Articles

Response of Surface Runoff and Sediment to the Conversion of a Marginal Grassland to a Switchgrass (Panicum virgatum) Bioenergy Feedstock System

The land systems between the humid and arid zones around the globe are critical to agricultural production and are characterized by a strong integration of the land use and water dynamics. In the southern Great Plains (SGP) of the United States, lakes and farm ponds are essential components in the land systems, and they provide unique habitats for wildlife, and critical water resources for irrigation and municipal water supplies. The conversion of the marginal grasslands to switchgrass (Panicum virgatum) biofuel feedstock for energy production has been proposed in the region. However, we have limited experimental data to assess the impact of this potential land-use change on the surface runoff, which is the primary water source for surface impoundments. Here, we report the results from a paired experimental watershed study that compared the runoff and sediment responses that were related to the conversion of prairie to a low-input biomass production system. The results show no significant change in the relationship between the event-based runoff and the precipitation. There was a substantial increase in the sediment yield (328%) during the conversion phase that was associated with the switchgrass establishment (i.e., the site preparation, herbicide application, and switchgrass planting). Once the switchgrass was established, the sediment yield was 21% lower than the nonconverted watershed. Our site-specific observations suggest that switchgrass biofuel production systems will have a minimum impact on the existing land and water systems. It may potentially serve as an environmentally friendly and economically viable alternative land use for slowing woody encroachment on marginal lands in the SGP.

Adventitious root culture of Plantago ovata Forssk. as a source of phenylethanoid glycosides

The investigations were targeted to obtain in vitro culture of Plantago ovata, which would be efficient in the production of plant biomass and phenolic compounds with multiple biological activities, like acteoside and plantamajoside - the main phenylethanoid glycosides present in the Plantago genus. In these experimental studies, roots were obtained by natural development from seedlings germinated in vitro and from in vitro multiplied shoots as well as by direct organogenesis on seedling leaf explants and indirect organogenesis from callus cultured on various explants. Callus-regenerated roots agitated in MS (Murashige and Skoog) liquid medium supplemented with phytohormones NAA (1-naphthaleneacetic acid) 0.25 mg/L and BAP (benzylaminopurine) 0.5 mg/L turned out to be a good growth system for root biomass production - mean increase of root fresh weight calculated on three following passages was 6641.07%. The quantitative screening of the root extract by HPTLC video densitometric method showed the content of acteoside 33.02 mg/g dry weight (d.w.) (538.9 mg/L of culture) and plantamajoside 6.39 mg/g d.w. (104.0 mg/L of culture) in root biomass obtained with the yield 16.32 g d.w. /L within 4 weeks. The content of those compounds in the in vitro shoots was significantly lower – 4.20 and 4.28 mg/g, d.w., respectively. Although the high level of acteoside in the root culture decreased in the following 8 weeks of the culture, it is still satisfactorily high (8.25 mg/g, d.w.). This is the first report on the adventitious root cultures of Plantago ovata and the content of those phenylethanoids in that well-grown plant material. The proposed approach provides an alternative to the soil-grown plants, source of plant metabolites, due to the possibility of the fast, regular and scalable production of plant biomass containing the compounds of interest as the main constituents.

Emergy-based sustainability analysis of bioenergy production from marginal and degraded lands of India

Analysing the sustainability of cultivating biomass and biofuel plant species on marginal and degraded lands is essential for assessing the socio-economic and environmental perspectives. Various approaches have been suggested for the sustainability analyses, such as life cycle assessment, footprint analysis, multi-criteria decision analysis, and emergy analysis. Among these approaches, the emergy analysis is one of the most direct methods to assess the system's sustainability. The present article was aimed to perform the emergy analysis to quantify the ecological impacts, bioenergy potential, socio-economic efficiency, and the sustainability of the bioenergy production systems. The emergy-based sustainability analysis was conducted for the Soyabean-, Pongamia-, Jatropha-based biodiesel and Tectona-based biomass production systems from the Indian marginal and degraded lands. Results depicted that under a set of system boundaries for each plant species, total emergy output (U) of 1000 kg biodiesel (biomass in case of Tectona) was calculated to be 0.99E+16 for Soyabean-; 1.01E+16 for Pongamia-; 1.33E+16 for Jatropha- and 0.72E+16 sej for Tectona-based bioenergy production options. Emergy of fuels dominated the economic inflows (F) (32.53%) under the Soyabean-based option making it the second system to represent a greater environmental load ratio (ELR) of 17.98. Furthermore, the emergy of water resources was dominated under F in other studied bioenergy options, i.e., 38.08% of F in Pongamia-, 44.54% in Jatropha-, and 66.52% in Tectona-based systems. The emergy sustainability indices (ESI) of 0.06, 1.04, 0.34, and 0.02 were found for Soyabean-, Pongamia-, Jatropha-, Tectona-based bioenergy production systems, respectively. Sensitivity analysis further suggested that a decrease of 3.5% in F resulted in a 10.02% increase of ESI for the Pongamia-based option. Pongamia-based options depicted an ESI > 1, which could be considered to have a sustainable contribution to the economy for medium periods. The estimated ESIs were fundamentally low because the systems were dependent mainly on the F.

Hydrogen Rich Product Gas from Air–Steam Gasification of Indian Biomasses with Waste Engine Oil as Binder

Production of hydrogen rich product gas through thermochemical energy conversion having the biomass gasification is making significant inroads for green hydrogen fuel generation. In the present work, detailed physical and chemical characterization, air and air–steam biomass gasification of four biomasses i.e., Kasai Saw Dust, Lemon Grass, Wheat Straw and Pigeon Pea Seed Coat from four different group of biomass production system at different steam to biomass ratio, equivalence ratio and with and without binder is analysed. Waste engine oil as an additive/binder is used. Experimental investigation for air and air–steam gasification is applied and compared. Product gas constituents, hydrogen production is examined with different steam to biomass (S/B) ratio and equivalence ratio. The equivalence ratio varies from 0.20 to 0.40 and the S/B ratio between 0 and 4. The waste engine oil (5 and 10 wt%) is mixed with the biomass during palletization. Results show maximum H2 production and HCV of product gas at an air to fuel of 0.26 and 2.4 steam to biomass ratio. This study considers the rarely studied Indian biomasses with waste engine oil as an additive for hydrogen-rich product gas production having small scale biomass gasifier.

Response of sediment concentration and load to removal of juniper woodland and subsequent establishment of grasslands – A paired experimental watershed study

Encroachment of woody plants into grasslands is a global phenomenon of environmental concern. Mechanical removal is often necessary to re-establish herbaceous dominance for heavily encroached watersheds, but its impact on water quality and quantity of runoff into streams and reservoirs has not been vigorously studied. The sediment concentration and load following mechanical removal of juniper (Juniperus virginiana, L.) woodland and subsequent re-establishment of tallgrass prairie or switchgrass (Panicum virgatum L.) biomass production were quantified at the experimental watershed scale in the south-central Great Plains, USA. Impact analysis was used to evaluate the effects of watershed treatment and phase of land use conversion. The annual sediment yield from juniper woodland watersheds averaged<0.10 t ha−1 yr−1 before treatment and increased to 0.28 t ha−1 yr−1 after juniper were cut and left on site. In the second year, removing the dried trees increased the annual sediment yield to 1.14 t ha−1 yr−1 in the prairie restoration watershed and 13.29 t ha−1 yr−1 in the switchgrass watershed that was sprayed with herbicide in preparation for no-till planting. The annual sediment loads averaged 0.44 t ha−1 yr−1 from the restored prairie and 0.29 t ha−1 yr−1 from the established switchgrass, comparable to 0.73 t ha−1 yr−1 from the intact juniper woodland during the third and fourth years after initiation of treatments.While restored grassland watersheds had elevated peak flows and longer flow duration leading to greater runoff, lower sediment yields were due to reduced mean and peak sediment concentration compared to the juniper watershed.Therefore, restoring juniper woodland to native prairie or switchgrass biomass production systems may increase water yield without increasing sediment yield, especially in years with extreme storm events.

Exploration of heavy metal uptake potential of three algal strains/consortia in suspended and attached growth systems

Three different algal strains/consortia; Chlorella pyrenoidosa (CP), consortium of Chlorella pyrenoidosa and Phormidium (PA6) and consortium from Hauz Khas lake (HL), were studied for their potential in heavy metals' bioremediation. Batch experiments (HRT-6 days) were performed in two different modes of algae cultivation systems; suspension and attached biofilms. The study aimed to highlight the suitability of an algal strain/consortium to different cultivation systems for metal removal and biomass production. The six commonly found heavy metals in wastewater; Cd, Cr, Pb, Cu, Ni and Zn, were used for the study. The selected algae were tested for its performance on individual and multiple metals contaminants. In individual metal spiked cultures (suspension), the common heavy metals that were uptaken efficiently by the three algal strains/consortia were Zn, Pb, Cu and Cd (>55%). Zn was uptaken >80% in all these test cultures. In mixed metal spiked suspension systems, all the metals were uptaken >60% by PA6 only. In mixed metal spiked attached systems, except for Cr, all other metals were uptaken efficiently by PA6 in the order Zn > Ni > Cd > Pb > Cu in the range of 78–98%. HL and CP performed best in suspension systems with individual metal spiking. PA6 performed better than HL and CP in mixed metal spiked media, especially in attached systems. The uptake of multiple metals from a variety of effluents can be done using PA6-like consortium (preferably in attached systems), whereas in effluents where only a single metal is present, CP/HL-like consortium can be used in suspended cultures.

Strategic deployment of riparian buffers and windbreaks in Europe can co-deliver biomass and environmental benefits

Within the scope of the new Common Agricultural Policy of the European Union, in coherence with other EU policies, new incentives are developed for farmers to deploy practices that are beneficial for climate, water, soil, air, and biodiversity. Such practices include establishment of multifunctional biomass production systems, designed to reduce environmental impacts while providing biomass for food, feed, bioenergy, and other biobased products. Here, we model three scenarios of large-scale deployment for two such systems, riparian buffers and windbreaks, across over 81,000 landscapes in Europe, and quantify the corresponding areas, biomass output, and environmental benefits. The results show that these systems can effectively reduce nitrogen emissions to water and soil loss by wind erosion, while simultaneously providing substantial environmental co-benefits, having limited negative effects on current agricultural production. This kind of beneficial land-use change using strategic perennialization is important for meeting environmental objectives while advancing towards a sustainable bioeconomy.

Development of an algal cell-attached solid surface culture system for simultaneous wastewater treatment and biomass production

Wastewater treatment using microalgae is receiving growing attention. Here, we have developed a portable tubular system containing an algal cell-coated solid surface for phosphorous recovery. P-depleted Chlorella cells attached to a solid surface removed phosphate from the medium about 70 times faster than P-replete cells. When the cell density was 20 g dry cell weight m−2 or less, P-depleted cells on the solid surface absorbed phosphate from the medium at almost the same rate as in liquid, the maximum capacity per solid surface area being about 6 mg P m−2 min−1. P in inorganic wastewater from chemical factories (ethanol factories; about 4 mg L−1) and in pond water (0.06 mg L−1) was mostly removed within 3 h with a simple device composed of a single solid-surfaced sheet (0.002 m−2) and a portable compact tubular device including 12 such sheets (totally 0.5 m−2), respectively. Simultaneously, cellular growth was confirmed with both wastewater and pond water. These findings suggested that the attached cell culture system, in which medium exchange to prepare P-depleted cells is much easier than in liquid cultures, is promising for dual use for biomass production and wastewater treatment.

Stimulating effects of cold plasma seed priming on germination and seedling growth of cumin plant

Improving germination and seedling establishment can effectively increase crop yields. Cold plasma (CP) seed priming can be used as an emerging tool to improve germination efficiency and increase seedling growth. The effects of CP seed priming for different time periods (5 and 10 min) on germination, seedling growth, seedling root morphology, photosynthetic pigments, antioxidant defense system and nutrient uptake of Cuminum cyminum L. (cumin) were investigated. Seed priming with 5 and 10 min CP improved the germination efficiency and germination index by increasing the water absorption capacity of the seeds. CP seed priming for 5 min induced growth, biomass production, proline content and antioxidant defense system of cumin seedlings. Seed pretreatment with 5 min CP enhanced nutrient uptake by increasing root growth, volume and area surface and, consequently, improved photosynthetic pigment contents and growth of cumin seedling. However, 10 CP pretreatment induced oxidative stress and damage to membrane lipids by excessively increasing the level of active species (H2O2 and superoxide anion), resulting in reduced seedling growth and biomass compared to control ones. Therefore, seed priming with CP at the appropriate time duration can be a promising tool to increase germination efficiency and improve seedling establishment in aromatic and medicinal plants.

Development of smart algae pond system for microalgae biomass production

The production of microalgae biomass is very promising as an alternative sustainable food, feed, high value biochemical, and 3rd generation biofuel. However, the use of microalgae biomass for the production of biofuel is still considered less feasible at this time. The main obstacle is the scale up of biomass production, high processing costs and low efficiency using the conventional biomass production system. Therefore, the use of advanced digital technology such as sensors, automation applications and the Internet of Things (IoT) was applied in this study. This research aimed to develop a Smart Algae Pond system equipped with three main functions of smart mixing, control of pH and CO2 supply, and the automatic harvesting system. The results revealed that the use of advanced digital technology and IoT could improve the productivity as well as control the production of biomass effectively and efficiently. The tested optimum value of pH was achieved at 8.5-9.5 with the CO2 concentration of 1 to 2% of the cultivation volume. Temperature was maintained from 25 to 35 °C, water velocity from 16 to 35 cm s−1, and air velocity of 8.33 cm3 s−1. Using the smart mixing system, the use of electrical energy was decreased from 0.5 to below 0.2 Kw/h. This study showed that microalgae biomass production can be measured using a water turbidity sensor.

The Impact of Poplar Short Rotation Coppice on Topsoil Physical Properties and Related Water Conditions

In Europe, the establishment of short rotation coppice (SRC) systems for biomass production has been expanding in the last decades. Several studies have considered the impacts of SRC on soil properties; many have focused on studying its effect on biochemical properties while only a few have addressed physical and hydraulic properties. This study reports the assessment of soil physical and hydraulic properties on two SRC sites on sandy soils planted with 3-year-old poplar trees and an adjacent conventional agricultural field in Western Slovakia. All sites contain a comparable sandy loam soil texture and both SRC fields differed only in the groundwater accessibility. Water infiltration experiments were conducted in the field with subsequent sampling of the upper topsoil (0–5 cm depth). The samples were further processed in the laboratory to obtain the water retention and hydraulic conductivity functions of the soil covering a wide range of soil pore saturation. These hydraulic functions were fitted by using the bimodal version of Kosugi-Mualem’s hydraulic model to estimate the pore-size distribution (PSD) of the soils. The comparison between the SRC field neighboring the agricultural field and the latter showed similar hydraulic soil properties such as the topsoil water retention. However, macropore content, bulk density (BD) and infiltration capacity differed under SRC particularly in the tree row. Analogously, the two SRC fields showed similar topsoil water contents. Other soil properties differed presenting an increased macropore content and higher BD in the SRC field with distant groundwater connection. Our findings suggest that the SRC management may influence the topsoil properties.

Apple-based agroforestry systems for biomass production and carbon sequestration: implication for food security and climate change contemplates in temperate region of Northern Himalaya, India

Agroforestry land use systems present a win–win opportunity by acting as carbon sinks while assisting in achieving food security, livelihood income and environmental amelioration. In this context, the present study was carried out at farmer’s field in central Kashmir region of India with the aim to acknowledge the potential of apple based agroforestry system for biomass production and carbon stock assessment for climate change mitigation. For conducting the study four intercrops viz., rajmash (Phaseolus vulgaris), green gram (Vigna radiata), french bean (P. vulgaris) and oats (Avena sativa) were intercropped with 11-year-old plantation of apple. The maximum total crop biomass was registered under control french bean and oats (7.85 t ha−1). Overall highest values of total biomass were observed under agroforestry system of apple + rajmash and Oats. The treatment, apple + rajmash and oats displayed highest values for both total tree biomass (29.16 t ha−1) and overall biomass of system (33.00 t ha−1). Maximum value of soil organic carbon (46.02 t ha−1) was observed under apple + green gram and oats. The highest ecosystem carbon was stored in the treatment involving the tree crop combination of apple + rajmash and oats (64.18 t ha−1) and is around 1.5 to 2 times higher than agriculture based system. The total ecosystem carbon in apple based land use system ranged between 53.23 and 64.18 t ha−1. These agroforestry systems in Himalayas can go a long way in augmenting the overall production and productivity by satisfying the rural livelihoods besides acting as effective carbon sink through carbon stockpiling and sequestration. The outcome of the present study can be significant in selecting different crop combinations for fruit based land use systems, future carbon studies, climate change contemplates, soil carbon stock estimation and land use planning along the lines of REDD + activities in other fragile Himalayan ecosystems.

Growth Analysis of Typha Domingensis after the Transplanting to a Floating System for Biomass Production

Growth Analysis of Typha Domingensis after the Transplanting to a Floating System for Biomass Production

Design, construction and performance of a quintuple renewable hybrid system of wind/geothermal/biomass/solar/hydro plus fuel cell

In this study, a hybrid system containing two main sections is designed, optimized, and constructed to make wind power more sustainable. Power generation section contains wind turbine (WT), alkaline electrolysis system (AES), biodiesel generator (BDG), and proton exchange membrane fuel cell (PEMFC), and water supply section for AES/PEMFC contains ground source heat pump (GSHP), microalgal culture pond (MCP), parabolic trough collector (PTC) and solar still desalination (SSD). First, light intensity, salinity, and air injection are investigated in the MCP system for maximum biomass production of 0.81 gL−1. In the PTC unit, operating fluid's flow rate, hybrid nanoparticles (MWCNT/MgO), and their ratios are considered for obtaining the highest thermal efficiency of 61.8%. Pressure, fluid flow rate, and still's height in the SSD unit are investigated for the highest water production of 23.1 Lday−1. Next, several AES based on different electrolytes are examined. Then, PEMFC with a maximum power density of 472 mWcm−2 is studied based on oxidant/polyaniline (PANI) ratio, PANI, and Pt amount as important parameters of the membrane-catalyst complex. Finally, catalyst, temperature, and reaction time are investigated for maximum biodiesel production of 81.4%. The capacity factor of the WT increases to 82.3% and the cost of electricity is 0.161 $kW−1h−1.

Microalgae Cultivation Technologies as an Opportunity for Bioenergetic System Development—Advantages and Limitations

Microalgal biomass is currently considered as a sustainable and renewable feedstock for biofuel production (biohydrogen, biomethane, biodiesel) characterized by lower emissions of hazardous air pollutants than fossil fuels. Photobioreactors for microalgae growth can be exploited using many industrial and domestic wastes. It allows locating the commercial microalgal systems in areas that cannot be employed for agricultural purposes, i.e., near heating or wastewater treatment plants and other industrial facilities producing carbon dioxide and organic and nutrient compounds. Despite their high potential, the large-scale algal biomass production technologies are not popular because the systems for biomass production, separation, drainage, and conversion into energy carriers are difficult to explicitly assess and balance, considering the ecological and economical concerns. Most of the studies presented in the literature have been carried out on a small, laboratory scale. This significantly limits the possibility of obtaining reliable data for a comprehensive assessment of the efficiency of such solutions. Therefore, there is a need to verify the results in pilot-scale and the full technical-scale studies. This study summarizes the strengths and weaknesses of microalgal biomass production technologies for bioenergetic applications.

Functional traits of individual varieties as determinants of growth and nitrogen use patterns in mixed stands of willow (Salix spp.)

Short rotation plantations of willows (Salix spp.) have high biomass production potential in many parts of the world, and may frequently support ecosystem services related to nutrient cycling. A plantation management enhancing favorable environmental impacts that are conducive to maintaining ecosystem services is a main challenge in establishing sustainable biomass production systems. There is evidence supporting the hypothesis that biomass production and nutrient cycling can be increased by supporting ecosystem niche differentiation (complementarity) through enhancing the number of plant species or varieties grown in the stand. However, the specific trait values of the individual components (e.g., varieties) in a mixed community could also be more important than the community diversity per se. We assessed, at community level, the plant trait profiles related to growth and nitrogen (N) use for four different Salix varieties that were taxonomically distinct at species or genotype level (‘Björn’, ‘Jorr’, ‘Loden’, ‘Tora’) and field-grown in unfertilized plots of pure and mixed communities during one cutting cycle in Central Sweden. The aims were to use elements of functional growth analysis for exploring the mechanistic relationships between various traits related to growth and N use at stand level in our pure and mixed willow communities; and to address two hypotheses related to (i) the effect of diversity level on above-ground traits linked to growth, N uptake efficiency, N productivity and N conservation; and (ii) the influence of individual variety identities on the growth and N use traits observed in a mixture. Diversity level had no significant effect on the traits assessed here, and we thus found no evidence in support of our hypothesis that traits linked to growth, N uptake and use are significantly affected by the diversity level per se. In most but not all cases, the admixing effects on trait values were explained by the effects of the individual variety characteristics assessed in monocultures in combination with their relative share in the respective mixtures. The absence or presence of individual varieties strongly affected community-averaged (stand level) trait values. Therefore, the design of desirable variety mixtures is suggested that combine, for example, the high nutrient conversion efficiency that certain varieties achieve in mixed stands with the specific nutrient acquisition characteristics of other varieties.

Water-energy nexus and greenhouse gas–sulfur oxides embodied emissions of biomass supply and production system: A large scale analysis using combined life cycle and dynamic simulation approach

The achievement of low or zero greenhouse gas and particulate matter emissions such as sulfur oxides, optimized water-energy nexus, and a well-protected environment are challenges that have become increasingly significant for the biomass industry. There is a need to conduct evaluation and analyses of the greenhouse gas and particulate emissions, water use and energy consumption of biomass process and delivery, from “cradle to gate”. Therefore, to fill this noted gap in the literature, this study aims to develop a combined life cycle and dynamic simulation model to examine water-energynexus in the biomass industry, particularly under uncertainties, as well as estimation of greenhouse gas and particulate matter emissions of the biomass supply chain by 2050. The dynamic modelling of material, energy, and water flows was used to perform those tasks. An in-depth analysis of environmental issues during the production, processing, conversion and delivery of empty fruit bunches biomass supply and production system is conducted. The model was tested and implemented through a case study of three main biomass suppliers in Malaysia. Comparison of environmental performance of the production stages of 31 products through pre-processed, intermediate, and final productions in the biomass supply chain shows that bio-compost, activated-carbon, and cellulose are the highest water users and energy consumers as well as the highest emitters of greenhouse gas and sulfur oxides for all the three suppliers. Sensitivity analysis was also conducted for these critical products based on recent governmental land and demand policies. The main finding of this paper indicates a need for a well-planned management of water-energynexus in pre-processed production compared to intermediate and final production of biomass supply chain. This finding provides valuable insights to the government agencies and stakeholders to pursue sustainable bioenergy development strategies.

Effective determination of biomass in oak coppices

The diameter at breast height of the largest sprout per coppiced stool proved to be accurate for the total sprout biomass estimates at stand level. Traditional coppicing is one of the oldest silvicultural systems for biomass production. However, a quick and simple biomass estimate methodology across the entire growth period is lacking. The objective of this study was to find the sprout parameters that need to be measured for accurate sprout estimates as well as to find a necessary minimum number of sprouts for these estimates. Using data from 20 sample Turkey oak multi-stem trees, we modelled sprout biomass as a function of an increasing number of sprouts in interaction with different sprout parameters in a later post-resprouting period. Results showed that the DBH of only two of the largest sprouts per stump proved to be accurate estimators of the total sprout biomass of the individual stool. For sprout biomass estimates at stand level, we recommend measuring the DBH of the largest sprout within each stool in a plot and then calculating and summing the estimated sprout biomasses of the individual stools. This study illustrates that the biomass can simply be estimated by easily measured parameters of sprouts; therefore, the multi-stemmed trees can be easily included into the yield or ecosystem studies of woody vegetation with less time-consuming measurements.

Nutrient removal by duckweed from anaerobically treated swine wastewater in lab-scale stabilization ponds in Vietnam

In Vietnam, swine wastewater is generally treated using anaerobic processes. Nevertheless, the level of pollutants in effluent after anaerobic treatment remains very high, thereby necessitating further treatment. This research was conducted to assess the applicability of duckweed (Lemna minor) for purifying wastewater collected from a household swine wastewater treatment system in Hanoi, Vietnam. After the anaerobically treated wastewater was diluted 10-fold, it was fed continuously to lab-scale stabilization ponds with and without planted duckweed at a hydraulic retention time of 5 days under ambient conditions. The chemical oxygen demand (COD), total nitrogen (T–N), and total phosphorus (T–P) concentrations in the influent were, respectively, 260–290 mg/L, 24–28 mg/L, and 1.4–1.8 mg/L. The COD, T–N, T–P removals in the pond with duckweed (74%, 84%, and 84%) were much higher than in the pond without duckweed (71%, 55%, and 58%). The duckweed greatly enhanced the first-order removal rates by 1.4, 2.0, and 3.2 times, respectively, for COD, T–N, and T–P in the ponds. Although the primary purification mechanisms in the ponds were sedimentation and adsorption, the duckweed grown with the relative growth rate of 0.07–0.16 d−1 showed nutrient uptake activity from the wastewater. Biofilms formed on the duckweed roots apparently promoted COD removal and degradation of organic nitrogen into ammonia. Stabilization ponds planted with duckweed are anticipated for use as co-beneficial systems for wastewater treatment and biomass production.

Ecological and Socio Economic Potential of Agroforestry: A Demonstration of Multi-story Agroforestry Practice in North Shewa Zone, Amhara Region

The homestead multistory agroforestry demonstration was conducted at Tarmaber district of North Shewa zone to demonstrate and evaluate model multistory agroforestry practice for its ecological and economic importance for the rural communities of the area. The demonstration in addition aimed to further enhance farmers' knowledge on this new cultivation method before any further adoption. The demonstration study was started in June 2013 as multistory agroforestry practices and established with special and temporal arrangements with three strata. The upper stratum comprised tree components, middle stratum was fruits and the lower stratum was different annual crops. The total area of a demonstration site was 0.045ha. Persea americana, Rhamnus prinoides, Coffea arabica, Musa paradisiaca, Phaseolus lunatus, Hibisicus sabdariffa and Vigna unguiculata were planted at different time of the lifetime of the study and yield data were collected. The results from this demonstration study showed that, on average 1507 kg of edible NTFPs harvested per hectare per year. Organic matter and available phosphorus were increased from 1.52 to 2.14%, and 4.26 to 15.98 ppm, respectively. In addition, this practice showed higher net present value (NPV) and benefit-cost ratio (B/C) than the two crop land 3537.36 US$ and 3.3 per ha from these different components. From this study it can be concluded that multistory agroforestry may be ecologically advantageous land use system for sustainable food, biomass production and economic return comparing with conventional agricultural practices. Therefore, future agricultural extension adoption should consider this homegarden agro-forestry practice for sustainable agricultural production and productivity especially in North Shewa areas where this practice is not well known.