Algae culture carbon footprint accounting method based on life cycle evaluation

Abstract

The invention belongs to the technical field of life cycle evaluation methods, and relates to a seaweed cultivation carbon footprint accounting method based on life cycle evaluation, and the life cycle evaluation method is used for evaluating various environmental loads of a seaweed cultivation system, namely kelp, undaria pinnatifida, laver, eucheuma and gracilaria. First, a life cycle boundary of a seaweed culture system is determined. Secondly, data such as material input, energy consumption and waste discharge of the system are collected, and life cycle list analysis is carried out; then, modeling is carried out on the breeding system by utilizing GaBi software, and the environmental influence of the breeding system is quantified by adopting a ReCiPe 2016 v1.1 Midpoint (H) method; and finally, comprehensively analyzing the result, identifying key links influencing carbon emission, and providing corresponding optimization and improvement measures. The invention provides a scientific basis for low-carbon development of global seaweed breeding industry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of life cycle assessment method, and relates to a seaweed cultivation carbon footprint accounting method based on life cycle assessment. BACKGROUND

[0002] With the increasingly serious global climate change problem, reducing greenhouse gas emissions has become the focus of global attention. Large-scale cultivated seaweed can not only serve as a low-carbon and sustainable future food source, but also play an important role in climate change mitigation strategies. However, current research on emission reduction paths in global food systems mainly focuses on land-based food systems (such as grain and livestock products), and the climate change load and emission reduction benefits of blue food from the ocean, especially large-scale cultivated seaweed, have not been fully evaluated.

[0003] Due to the growing demand, seaweed cultivation is expanding worldwide, and seaweed cultivation has great potential. Currently, life cycle assessment (LCA) studies of large-scale cultivated seaweed mainly focus on high-yield kelp, and there is a lack of systematic evaluation of varieties such as nori, dragon's blood and Gracilaria. It is worth noting that although the yield of Undaria pinnatifida accounts for a small proportion, it has been identified and included in the important "Future Food" list, and its cultivation sustainability has gradually attracted attention in recent years.

[0004] In recent years, there have been many life cycle assessment studies on seaweed cultivation and its preservation system in relation to seaweed and its related derivative industries, such as seaweed food and seaweed protein, bio-refining, bio-extraction, bio-fuel or fuel derivatives. However, these studies mainly focus on calculating the overall environmental impact of seaweed derivative products, and there are relatively few analyses and related improvement suggestions for seaweed cultivation itself, and the data collection for the seaweed cultivation process is not perfect. It should be emphasized that among the multiple uses of seaweed as feed, fuel, chemical raw materials and food, food use has been proven to be the most cost-effective path for greenhouse gas emission reduction. Therefore, quantitatively comparing the life cycle carbon footprint of different seaweed foods is very important for the low-carbon transformation of agri-food systems. SUMMARY

[0005] To solve the above problems, the present application takes large seaweed (kelp, Undaria pinnatifida, nori, dragon's blood and Gracilaria) as an example and proposes a method for analyzing the environmental impact of seaweed cultivation system to comprehensively evaluate the carbon emission of seaweed cultivation.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] A seaweed cultivation carbon footprint accounting method based on life cycle assessment, the steps are as follows:

[0008] Step (1) Scope and Objectives: Based on the common practice in the seaweed aquaculture industry of using wet weight as the unit of economic output measurement, the functional unit of LCA is defined as "producing 1 ton of wet weight seaweed". This choice of functional unit not only conforms to industry practice but also enhances the comparability of research results among similar systems and with other terrestrial crop or food production systems. The system boundary of this invention is set as "cradle to gate", covering the key stages of the entire seaweed aquaculture process, including seedling cultivation, temporary holding, growth, and harvesting. Among the various environmental impacts generated by the system, this invention focuses on assessing the climate change effects caused by greenhouse gas emissions.

[0009] Step (2) Inventory Analysis (LCI): The inventory data comes from field surveys conducted in the main seaweed farming areas of the study region and relevant literature data. It mainly includes data on seaweed farming-related material consumption (such as farming ropes, wooden stakes, stone blocks, buoys, etc.) and energy consumption. It is worth noting that the units used to calculate seaweed yield data are inconsistent. For example, the yields of kelp, wakame, and sea lettuce are calculated per unit seedling rope length (kg / m), laver per unit net area (kg / net), and Gracilaria per unit farming area (kg / ha). To facilitate comparison, all yield data are standardized to the functional unit of 1 ton of wet-weight seaweed. This standardization helps with subsequent modeling analysis and facilitates comparison with existing literature data. Based on this, the inputs related to materials and energy in each farming stage are further quantified to construct a complete life cycle inventory.

[0010] Step (3) Impact Assessment: This invention uses the ReCiPe v1.10 Midpoint (H) life cycle impact assessment method to evaluate the greenhouse gas emissions generated by the seaweed aquaculture system during its life cycle. This method converts various greenhouse gas emissions into global warming potential (GWP) and uses carbon dioxide equivalent (kgCO2e) as the unit of measurement to achieve quantitative characterization of climate change. The life cycle modeling and characterization process was completed on the GaBi software platform. The background data came from the GaBi commercial database, the prospective data was mainly based on field surveys in the study area, and the missing data was supplemented by relevant literature.

[0011] The method for calculating the carbon footprint of seaweed is as follows:

[0012]

[0013] In the formula: Carbon footprint of seaweed, kgCO2e; For the breeding process Chinese activities The activity level, kg or kWh, where, for the process 1 represents seedling cultivation, 2 represents temporary rearing, 3 represents growth, and 4 represents harvest; for activities 1 represents electricity production, 2 represents fertilizer production, 3 represents seawater introduction, 4 represents wastewater treatment, 5 represents aquaculture rope production, 6 represents buoy production, 7 represents fixed base production, and 8 represents diesel production and combustion. The greenhouse gas emission factor is kgCO2eq / kg or kgCO2eq / kWh.

[0014] Step (4) Results Analysis: Integrate the results of inventory analysis and impact assessment to systematically evaluate the carbon footprint composition throughout the entire seaweed farming process. Through sensitivity analysis, identify key inputs that significantly contribute to the climate load of seaweed products. Based on the conclusions of the sensitivity analysis and actual farming conditions, further scenario analysis will be conducted to explore feasible technologies or management measures to reduce the climate impact of seaweed farming systems and provide a scientific basis for the formulation of low-carbon farming strategies.

[0015] The beneficial effects of this invention are:

[0016] (1) Through the life cycle assessment (LCA) method, the present invention can comprehensively and accurately quantify greenhouse gas emissions (carbon footprint) throughout the entire process of seaweed farming.

[0017] (2) According to the evaluation results of the present invention, the environmental load of the seaweed farming system can be significantly reduced by replacing the fixed base and extending the service life of the materials, thereby promoting the transformation of the blue food system towards a climate-friendly direction.

[0018] (3) The carbon emission assessment and optimization strategy proposed in this invention has important guiding significance for seaweed farming enterprises and provides scientific decision-making basis for policymakers. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the evaluation boundary for carbon footprint accounting of seaweed farming. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described in conjunction with the technical solutions and accompanying drawings.

[0021] This embodiment systematically analyzes the carbon footprint of seaweed cultivation using the life cycle assessment (LCA) method. For example... Figure 1 As shown, the life cycle boundary includes stages such as seaweed seedling cultivation, temporary holding, cultivation, harvesting, recycling and disposal of waste plastics, and related energy consumption. Carbon emissions from raw materials and transportation are ignored. Data are derived from field surveys of seaweed farms and relevant literature.

[0022] Kelp and wakame seaweed are cultivated using similar methods, primarily employing longline or floating raft cultivation. Nori seaweed grows in the intertidal zone and is cultivated using net curtains. Based on tidal exposure requirements, nori seaweed cultivation is categorized into fixed net cultivation, semi-floating cultivation, and fully floating cultivation. The cultivation methods for *Echinochloa crus-galli* and *Gracilaria zebrina* vary depending on water depth, typically using suspended longline or floating raft cultivation. The system boundary includes energy, resource, and material inputs, such as cultivation ropes (floating ropes, pegs, hanging ropes, seedling ropes, float-binding ropes), buoys, anchoring bases (wooden pegs or stone weights), bamboo, electricity, fertilizer, and fuel oil. Fuel oil is primarily used for daily marine management and seaweed harvesting, while fertilizer and electricity are used for seedling cultivation. This embodiment covers the process up to the harvest stage and excludes downstream stages (such as drying, processing, and distribution).

[0023] This invention employs the life cycle assessment (LCA) method to quantify the global warming potential of five macrocultivated seaweed species. Among them, kelp (91-154 kgCO2e t) -1 ) and wakame (103-189 kg CO2e t) -1 Comparable to, and higher than, *Euphorbia tirucalli* (28-43 kg CO2 e t). -1 ) and Gracilaria (33-107 kgCO2e t) -1 (), lower than that of laver (176-258 kgCO2e t) -1 The anchoring materials (such as bobbins) in aquaculture facilities are the largest contributor to the GWP (41-61%) of kelp and wakame systems, accounting for as much as 65% in some regions. Optimizing anchoring materials and extending the lifespan of polyethylene ropes are important emission reduction pathways that can reduce the GWP of kelp and wakame aquaculture systems by 53-66%.

[0024] This embodiment quantifies the environmental impacts of five seaweed farming systems throughout their life cycles, identifies key substances causing these impacts, and proposes improvement suggestions. It provides a more systematic and comprehensive understanding of seaweed farming systems and analyzes the contribution of each stage of the life cycle to the overall environmental impact, thereby improving the environmental sustainability of seaweed farming. The research results contribute to providing green development solutions for the seaweed farming industry and promoting its role in global climate change mitigation.

Claims

1. A method for accounting for carbon footprint of seaweed farming based on life cycle assessment, characterized by, The steps are as follows: Step (1) target and scope determination: the basic functional unit is determined as "producing 1 ton of wet weight seaweed"; the system boundary covers the key stages in the whole process of seaweed cultivation, including seedling, temporary cultivation, maturation and harvesting; Step (2) inventory analysis: the inventory data is derived from field research in the main seaweed cultivation areas in the study area and relevant literature data, including seaweed cultivation related material consumption and energy consumption data; all yield data is standardized to 1 ton of wet weight seaweed functional unit; Step (3) impact assessment: the ReCiPe v1.10 Midpoint (H) life cycle impact assessment method is selected to assess the greenhouse gas emissions generated by the seaweed cultivation system in the life cycle; by converting various greenhouse gas emissions into global warming potential GWP, and taking carbon dioxide equivalent as the unit of measurement, the quantitative characterization of climate change is realized; Step (4) result analysis: integrate the results of inventory analysis and impact assessment, and systematically evaluate the carbon footprint composition in the whole process of seaweed cultivation; through sensitivity analysis, identify the key material inputs that significantly contribute to the climate load of seaweed products; combined with the conclusions of sensitivity analysis and actual cultivation situation, further carry out scenario analysis, explore the feasible technical or management measures to reduce the climate impact of seaweed cultivation system, and provide scientific basis for the development of low-carbon cultivation strategy.

2. The seaweed cultivation carbon footprint accounting method based on life cycle assessment according to claim 1, characterized in that The seaweed cultivation related materials include cultivation ropes, wooden pegs, stone blocks and floating balls.

3. The seaweed cultivation carbon footprint accounting method based on life cycle assessment according to claim 1, characterized in that The calculation method of seaweed carbon footprint is as follows: ； wherein: is the seaweed carbon footprint, kg CO2e; is the farming process is the activity level of the activity , kg or kWh, wherein for the process 1 stands for hatchery, 2 for temporary holding, 3 for grow-out, 4 for harvest; for the activity 1 stands for electricity production, 2 for fertilizer production, 3 for seawater intake, 4 for wastewater treatment, 5 for farming rope production, 6 for float production, 7 for fixed base production, 8 for diesel production and combustion; is the greenhouse gas emission factor, kg CO2eq / kg or kg CO2eq / kWh.

4. The method according to claim 1, wherein, In step (3), the life cycle modeling and characterization process is completed on the GaBi software platform, wherein the background data is derived from the GaBi commercial database, the foreground data is based on field research in the study area, and the missing data is supplemented by relevant literature.

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