An Overview of Algae for Biodiesel Production Using Bibliometric Indicators

Table 7

Most frequently occurring keywords.

SN	Keyword	Occurrences	Total link strength
1	Biodiesel	465	997
2	Microalgae	283	584
3	Transesterification	146	331
4	Algae	87	237
5	Extraction	76	177
6	Lipids	55	164
7	Ethanol	47	174
8	Biomass	45	98
9	In situ transesterification	42	96
10	Biorefinery	34	132
11	Chlorella vulgaris	31	74
12	Microwave irradiation	26	67
13	Optimization	26	62
14	Heterogeneous catalyst	23	64
15	Lipase	23	50
16	Algae oil	22	53
17	Fatty acids	18	30
18	Fermentation	18	43
19	Microalgae oil	18	37
20	Biogas	17	53
21	Response surface methodology	17	34
22	Catalysis	15	35
23	Hydrogen	15	100
24	Renewable energy	15	18
25	Wastewater	15	30
26	Bio-oil	14	46
27	Biohydrogen	14	42
28	Cell disruption	14	35
29	Methanol	13	22
30	Wet microalgae	13	20
31	Kinetics	12	35
32	Ultrasound	12	30
33	Pyrolysis	11	37
34	Cyanobacteria	10	25
35	Esterification	10	25
36	Ionic liquid	10	26
37	Sustainability	10	22
38	Butanol	9	73
39	Emission	9	21
40	Feedstocks	9	74
41	Lignocelluloses	9	85
42	Methane	9	69
43	Nannochloropsis oculata	9	21
44	Process integration	9	10
45	Supercritical methanol	9	27
46	Wet algae	9	22
47	Chlorella protothecoides	8	17
48	Ultrasonication	8	19
49	Chlorella sp.	7	14
50	Photobioreactor	7	24